attocube systems :... Ballistic electron emission microscopy (BEEM) studies using ANP100 nanopositioners APPLICATION NOTE P09 RELATED PRODUCTS G

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1 APPLICATION NOTE P09 Ballistic electron emission microscopy (BEEM) studies using ANP100 nanopositioners Electrical injection, transport, manipulation and detection of spin polarized electrons in a semiconductor are essential requirements for utilizing the spin degree of freedom in a future semiconductor spintronics technology. One suitable instrumental technique hereby is the ballistic electron emission microscopy (BEEM) which allows simultaneous measurements of the tunneling current and a resulting ballistic current entering the semiconductor. tip collector spin valve basis ANPxyz100 A research team from the Department of Physics at the University of Regensburg in Germany is using the tip of a scanning tunneling microscope as an injector of hot electrons or holes into spin valves as well as into cleaved edge overgrown heterostructures. Recently, they have studied the spin-dependent transport of injected and hole excited electrons through epitaxial spin valves in an external magnetic field at room temperature (1). Fig. 1: Photo of the BEEM setup. AlGaAS GaAS BEEM Figure 1 shows such a STM/BEEM instrumental setup where the attocube ANPxyz100 nanopositioners are implemented enabling the coarse positioning of the sample. This positioning stack offers a travel range of 7 x 7 x 6 mm by having a size of 24 x 24 x 53 mm and is also applied to establish the tunneling contact between the STM tip and the sample. The scanning process itself is performed by a dedicated tube scanner. Figures 2 and Figures 3 describe previous results when scanning across a GaAs/AlGaAs heterostructure, which has been cleaved and overgrown with an iron and gold layer. For instance, when applying high tunneling voltages of 2.5 V the various GaAs and AlGaAs sections can be clearly seen due to differences of approx. 300 mev in the Schottky barrier heights The ANPxyz100 stepper positioners (Figure 2). These differences result in variations of 800 fa in the collector current. Figure 3 clearly exhibits the differently obtained image types. Au Fe 2 µm n-gaas Emitter 500 nm n-gaas n-algaas µm n-algaas nm n-gaas n-algaas Fig. 2: Au/Fe on a GaAs/AlGaAs heterostructure a) schematic cross section of the sample, b) BEEM measurement with I T = 25 na, E = 2.5 V, (2 x 2 µm scan). STM n-gaas nm n-gaas GaAs BEEM AlGaAs GaAs These results are another demonstration of the reliable performance and stability of attocube s ANPxyz100 nanopositioner stack for STM and STM-like applications. Reference: (1) E. Heindl et al., Ballistic electron magnetic microscopy on epitaxial spin valves, Phys. Rev. B, 75, (2007). The data was generously provided by E. Heindl from the Department of Physics, University of Regensburg, Germany. attocube systems explore your nanoworld Fig. 3: Comparison of image contrast for STM (topographical effects) and BEEM measurements (different Schottky barrier heights) when performing a 150 x 150 nm scan. ANPx100 ANPz100 ANC150/3 Linear, horizontal stepper positioner Linear, vertical stepper positioner Piezo step controller attocube systems AG All rights reserved.

2 nanotooling Solutions for extreme Environments Vibration analysis of a positioner (ANPz101) using the attofpsensor A vibrometer setup using the attofpsensor has been characterized in a static vibrometry configuration (i.e. no vibration is excited). The sensitivity of the setup is shown and the striking stability of an ANPz101 is demonstrated. The schematic of the setup is given in Fig. 1. A Si sample is placed on a Ti holder that is fixed on an ANPz101 and a piezoelectric vibrating plate. A cleaved 250 µm outer diameter optical fibre is placed in a ferrule and approached to the sample to form a cavity of a few microns size. Using the LDM1300 laser/detector module, laser light is guided into the cavity and the back-reflection from the low-finesse Fabry-Perot cavity is measured. A variation in the cavity length gives rise to a quasi-sinusoidal interference pattern in the detected sensor intensity. Using a piezoelectric stack, the ferrule holder position can be tuned to be at the maximum of the sensor sensitivity. This corresponds to the linear part of the observed sinusoidal interference pattern. Derived from the relation given in [1], one can convert the optical signal into displacement: δx=(λ/2π)δi/i 0, where δx is the displacement in [nm], λ is the laser wavelength in [nm], δi is the intensity variation due to the vibration in [V] and I 0 is the overall contrast of the sinusoidal signal in [V]. A Fast Fourier Transform (FFT) of the attofpsensor output signal directly allows measuring the overall system stability. The outcome of the experiments is given in Fig. 2 i) to iii). Vibrations lower as 2 Å/ Hz can be clearly detected between 0 and 10 khz while the background signal is at most of only 20 pm/ Hz. For calibration purpose, the system has been excited with a fixed frequency sine-wave voltage. This gives rise to the test peaks in the results and shows the noteworthy detection sensitivity of the setup. In these measurements, few of the impressive capabilities of the attofpsensor have been explored (here in a bare-fiber, static vibrometer setup). The setup comprising an attocube ANPz101 positioner proves to have better stability than 2 Å/ Hz between 0 and 10 khz. These measurements were performed by K. Karrai and P.-F. Braun in the attocube application labs. [1] D. Rugar, et al., Appl. Phys. Lett. 55, 2588 (1989) piezo stack sliding block single-mode fiber base plate ANPz101 ceramic ferrule (Ø 2.5 mm) Si sample Ti holder piezo stack Fig. 1: Schematic of the measurement setup. amplitude (pm/ Hz) amplitude (pm/ Hz) i) 0.2 nm test peak frequency (Hz) ii) 12 pm test peak frequency (Hz) attofpsensor ANPz101 LDM1300 attocube fiber probe sensor in vibrometry configuration linear, vertical stepper positioner laser detector module for 1310 nm 8 pm test peak Fig. 2: Vibration as a function of frequency in the vibrometer setup. i) very low frequency range up to 5 Hz, ii) low frequency range up to 100 Hz, iii) frequency range up to 10 khz. amplitude (pm/ Hz) 20 2 iii) frequency (khz) attocube systems AG All rights reserved.

3 APPLICATION NOTE P10 UHV-Compatibility of encoded attocube rotator ANR101/RES/UHV with vacuum of up to 8*10-11 mbar Experiments in Ultra High Vacuum (UHV) conditions require highest precision and care in manufacturing of the respective equipment. The outgassing behavior is a crucial factor when researchers decide for new instruments in their setups. This application note describes measurements of the outgassing data of an attocube rotator with an integrated resistive encoder ANR101/RES/UHV (see Fig. 1). The tests were carried out at the BESSY synchrotron facility in Berlin, Germany. The tests were split in two parts: a) Measurement of the reference mass spectrum of the empty vacuum chamber (green curve in Fig. 2) b) Measurement of the mass spectrum of the vacuum chamber after inserting the attocube rotator (blue curve in Fig. 2). Fig. 1: attocube rotator ANR101/RES/UHV with an integrated resistive encoder. The /UHV model is specified for vacuum conditions of up to 5*10-11 mbar and is bakeable to up to 150 C. The vacuum chamber was baked out for three days at a temperature of 180 C. The turbo pump used had a pumping power of 180 l/s for N 2. After cooling down to room temperature a pressure of 7.3*10-11 mbar was measured and a mass spectrum was taken. Afterwards the rotator ANR101/RES/UHV was inserted into the vacuum chamber and baked out again for three days at 100 C. Due to this procedure an end pressure of 8*10-11 mbar could be achieved. The measured mass spectrum is shown in Fig. 2 (blue curve). The third (brown) curve in Fig. 2 illustrates the difference between both mass spectra. This curve shows emissions added by the rotator; these are at remarkably small levels. The peaks that are visible in the spectrum mainly refer to H 2 O, CO, N 2, and CO 2, i.e. elements that were present in the chamber before. It is expected that these peaks can be further reduced by an increased bake out temperature and duration. In summary, this means that the positioner is perfectly suited for UHV use. These experiments are an example for the outstanding UHV compatibility of the attocube systems positioning systems which are specified to pressures down to 5*10-11 mbar. The data was generously provided by Christian Kalus (christian.kalus@bessy.de) and Stefan Eisebitt (eisebitt@bessy.de), BESSY GmbH, Albert-Einstein-Str. 15, Berlin, Germany attocube systems explore your nanoworld Fig. 2: UHV outgassing data measured at BESSY synchrotron facility in Berlin. Blue curve: mass spectrum of the vacuum chamber with an ANR101/RES/UHV inside. Green curve: reference mass spectrum of the empty vacuum chamber. Brown curve: Difference of both mass spectra. The peaks refer to additional emissions caused by the ANR101/RES/UHV. ANR101/RES/UHV ANC150/1 high precision, piezo electric, inertial rotator for big loads electronic controller attocube systems AG All rights reserved.

4 APPLICATION NOTE P11 Angle-dependent transport measurements at high magnetic fields and mk temperatures with attocube systems rotator ANR30/LT Based on an attocube systems rotator ANR30/LT (see Fig. 1) a rotation stage for angle-dependent transport measurements in magnetic fields up to 33 Tesla and temperatures down to 40 mk was built at the user facility of the High Field Magnet Laboratory in Nijmegen. The mixing chamber of the commercially available dilution refrigerator from Leiden Cryogenics offers only a limited space of 17 mm in diameter. Hence, the ultra compact attocube rotator ANR30/LT is the positioner of choice for this task. Fig. 2 shows the rotator which is fi x ed on a plastic (Hysol) dilution refrigerator insert. Fig. 1: Ultra compact attocube rotator ANR30/LT with 10 mm diameter and 9 mm height. The angular movement of the ANR30/LT is transmitted via a thin copper wire (100 µm diamter) to a rotating sample stage with a home-made 20-pin spring-contact socket for samples mounted into standard LCC-20 packages. The contacts are connected to a fixed 40-pin connector of the dilution refrigerator using copper wires with a diameter of 30 µm to minimize the mechanical load on the rotator. The voltage pulses which are needed for driving the rotator are supplied via the same 40-pin connector using two parallel wires for each contact. Due to the small capacitance of the ANR30/LT of only 14 nf at low temperatures, the relatively high resistance of the cabling of approx. 36 Ohm in total does not raise a problem for the rotator. The additional LEDs which are also marked in Fig. 2 enable excitation of additional carriers in semi-conductor samples. A GaAs-heterostructure Hall-bar was mounted onto the described insert and the angle dependent Quantum Hall Effect between 0 and 52 degrees was measured at a temperature of 40 mk (see Fig. 3). At θ = 0 the sample is oriented perpendicular to the magnetic field. A driving voltage of 70 Volts at f = 1000 Hz was used to rotate the sample. During a typical rotation by a few degrees, lasting several seconds, the dilution refrigerator warmed up only a few tens of mk and its temperature never exceeded 100 mk (independent of rotation time). The step size at these low temperatures and the conditions above was measured as / degrees. The angle covers a range from +110 degrees to -50 degrees, only limited by the contact wires mechanical load. Fig. 2: Setup for angle dependent transport measurements with an attocube rotator ANR30/LT which is inserted in a dilution refrigerator. The data and application note was generously provided by: A. J. M. Giesbers, and U. Zeitler, High Field Magnet Laboratory, Nijmegen, The Netherlands. ANR30/LT ANC150/3 ultra compact, high precision, piezo electric, inertial rotator piezo step controller attocube systems explore your nanoworld Hall Resistance (kω) θ = 0 θ = Magnetic Field (T) Fig. 3: Angle dependent measurements of the Quantum Hall Effect in an AlGaAs two-dimensional electron gas. attocube systems AG All rights reserved.

5 APPLICATION NOTE P12 Manipulating Carbon Nanotubes using attocube ANPxyz50 Positioners in a Scanning Electron Microscope Attaching Carbon Nanotubes (CNTs) on metal tips is an attractive method for functionalizing tips or for further experiments on these nanoscale objects. This application note describes experiments on attaching such nanotube bundles onto a Tungsten tip in a scanning electron microscope (SEM) using attocube ANPxyz50/HV positioners. The setup consists of three positioning stages carrying the sample with the CNTs and the tip on a special adapter plate (see Fig. 1). On the left, one can see the ANPz50 positioner that carries the tip. On the right, two ANPx50 positioners with orthogonal orientation have been placed to position the sample. The tip is formed by an etched Tungsten tip, while the sample is a slotted silicon chip, across which CNTs have been synthesized in a floating CVD system. The tip can be aligned with regards to the sample in all three dimensions, while the height of the sample stays constant with regards to the electron microscope to keep it focussed. Additional ground wiring has been attached to the positioners bodies to avoid electrical charging due to the electron beam (it has to be noted that the attocube positioners due to their design are electrically isolating from the top to the base). The setup was directly mounted on the motorized sample stage of the SEM with the electrical wiring fed through a flange in the door of the SEM. The workflow of the attachment was as follows: After identifying a thin bundle of CNTs across the slit, the tip was positioned close to the bundle in order to allow attachment by van der Waals forces. After tearing the bundle apart by subsequent tip retraction, a short part of the bundle was left attached to the tip (see Fig. 2). Fig. 1: Sketch of the setup. The positioners have been grouped as xy and z in order to minimize the height of the setup. In summary, it has been shown that the attocube systems ANPxyz50 positioners can easily be mounted into a commercial SEM for precise manipulation experiments. The orthogonal setup of the attocube ANPxyz50 positioners greatly facilitated the whole attachment process. Thin Carbon Nanotube bundles could be selected and attached to metal tips, thus enabling further experiments with these functionalized tips. The experiments have been performed by Sebastian Stapfner, Song Li, and Eva Weig from the nanophysics group at the Ludwig-Maximilians- University of Munich (LMU). attocube systems explore your nanoworld Fig. 2: Process of attaching a Carbon Nanotube bundle: a) bringing the tip close to the bundle. b) bundle attaches to the tip by van der Waals forces, c) and d) the bundle ruptures as the tip is moved away. ANPxyz50/HV ANC150/3 RELATED PRODUCTS ultra compact, high precision, piezo electric, inertial positioners piezo step controller attocube systems AG All rights reserved.

6 APPLICATION NOTE P14 Dissipation in Optomechanical Resonators Quantum optomechanics [1-3] is a rapidly expanding field of research, combining quantum optics with optomechanical coupling in order to generate and detect quantum states of micro- and nanomechanical devices. Recent experiments have demonstrated mechanical laser cooling down to the level of only a few thermal quanta [4-8] and theory predicts that the quantum ground state can be reached with this method [9-11]. At present, however, the rate of thermalization prevents laser cooling to the vibrational ground state. In order to overcome this barrier, the impact and sources of mechanical damping in these devices must be quantified. In this application, G.D. Cole and M. Aspelmeyer of the University of Vienna have analyzed the acoustic disspiation of microresonators using a cryogenic interferometry setup, see Fig. 1. In detail, their system utilizes a continuous flow 4 He cryostat as sample chamber equipped with a stack of attocube s ANPxyz51 positioners for aligning the sample with respect to an optical fiber. This fiber is part of a homodyne interferometer, allowing high signal-to-noise measurements of the eigenmodes of the resonator (Fig. 2) while keeping disturbances due to radiation pressure and optical fluctuations at a minimum. The turbo-pumped cryostat enables interrogation from room temperature (RT) to 20 K, and from atmospheric pressure to vacuum levels of millibar. Cole & Aspelmeyer take advantage of a piezo-electric disc to excite the optomechanical resonator, either broad band by white noise or resonant at a specific frequency. While the first method allows to characterize the resonance spectrum of the resonator, the second accurately yields the ringdown time for a single resonance and therefore its quality factor Q. Fig. 3 depicts this information for a resonator eigenmode with a frequency close to 4 MHz, demonstrating a Q factor of To simultaneously achieve high Q and high reflectivity, the optomechanical resonators are fabricated from an epitaxial Al x Ga 1-x As Bragg reflector. This technique results in reflectivities exceeding 99.98% at 1064 nm, providing the basic requirement for optical ground-state cooling. Fig. 1: Schematic of the experimental setup: the sample chip (green) is placed in a continuous flow 4 He cryostat and positioned underneath an optical fiber using an ANPxyz51 positioner stack. The resonator is piezoelectrically excited and its vibrational modes are detected using homodyne fiber interferometry (not shown). Fig. 2: Scanning electron microscope image of the optomechanical resonator, fabricated from epitaxially grown Al x Ga 1-x As. In summary, an experimental setup used to characterize the properties of a micro-optomechanical resonator with resonance frequencies of up to 4 MHz and Q-factors as high as is described in this application note. A stack of attocube ANPxyz51 positioners is used to precisely position the resonator with respect to an optical fiber, forming one arm of a homodyne interferometer. References: [1] M. Aspelmeyer and K.C. Schwab, New J. Phys. 10, (2008). [2] T. J. Kippenberg and K. J. Vahala, Science 321, 1172 (2008). [3] F. Marquardt and S. M. Girvin, Physics 2, 40 (2009). [4] S. Gröblacher, J. B. Hertzberg, M. R. Vanner, G. D. Cole, S. Gigan, K. C. Schwab, and M. Aspelmeyer, Nature Phys. 5, 485 (2009). [5] A. Schliesser, O. Arcizet, R. Rivière, G. Anetsberger, and T.J. Kippenberg, Nature Physics 5, 509 (2009). [6] T. Rocheleau, T. Ndukum, C. Macklin, J.B. Hertzberg, A.A. Clerk, and K.C. Schwab, Nature 463, 72 (2010). [7] S. Gigan, H.R. Böhm, M. Paternostro, F. Blaser, G. Langer, J.B. Hertzberg, K.C. Schwab, D. Bäuerle, M. Aspelmeyer, and A. Zeilinger, Nature 444, 67 (2006). [8] O. Arcizet, P.-F. Cohadon, T. Briant, M. Pinard, and A. Heidmann, Nature 444, (2006). [9] I. Wilson-Rae, N. Nooshi, W. Zwerger, and T.J. Kippenberg, Phys. Rev. Lett. 99, (2007). [10] F. Marquardt, J.P. Chen, A.A. Clerk, and S.M. Girvin, Phys. Rev. Lett. 99, (2007). [11] C. Genes, D. Vitali, P. Tombesi, S. Gigan, and M. Aspelmeyer, Phys. Rev. A 77, (2008) Fig. 3: Experimental ringdown of a 100x50 µm² resonator stack measured at 20 K and 2.5 x 10-7 mbar. The exponential fit (red) yields a Q value of Fig. 1-3 courtesy of G.D. Cole/M. Aspelmeyer, Univ. of Vienna. ANPxyz51/LT/HV linear stepper positioners providing highest stability ANC300/3 piezo positioning controller attocube systems AG All rights reserved.

7 APPLICATION NOTE P15 3D g-factor mapping of single quantum dots In this application, M. Ediger and R. T. Phillips from Cavendish Labs at Cambridge University in UK report on a novel fibre-based confocal microscope [1] to investigate the properties of nanostructures such as InGaAs quantum dots (QDs) via magneto-photoluminescence (PL). The design allows them to turn the samples to arbitrary angles of tilt and rotation with respect to a magnetic field of up to 10 T at low temperatures, while maintaining focus on a single QD. Modelling the exciton emission [2] they can extract the full 3-dimensional g-factor tensors for the electrons and holes and their exchange parameters. The new method improves upon the first studies of this type [3,4] by allowing dots to be selected in the microscope using the positioning capability. An integral part of this setup is a stack of four attocube nano-positioners consisting of an ANPz50, an ANR50 and two ANPx50 s; this stack is fixed to a rotatable mount by a gear mechanism (see Fig. 1). The ANR50 and the mount provide the two axes required to allow exploration of all orientations with respect to an applied magnetic field. Ediger & Phillips are able to make full use of the high spatial resolution of the positioners at any angle, which allows them to correct efficiently for the effects of gravity or diamagnetic shifts during parameter change in the experiments. On the other hand, the high stability of the motors is demonstrated by the ability to study the same structure at any angle over extended periods of time without loss of focus. The only effect of tilt on the operation of the motors is the transfer of the slight preferential down movement of the ANPz50 due to gravitation to one of the ANPx50. The example data in Fig. 2 shows the emission of the neutral exciton of a single InGaAs quantum dot tilted to 45 with respect to a magnetic field of 0 to 10 T at a temperature of 4 K. The intense upper doublet belongs to the bright exciton states, while the faint lines emerging at about 2 T stem from predominantly dark transitions that only become visible due to a field-induced mixing with the bright states. For standard magneto- PL in Faraday geometry (0 tilt) this mixing would not appear for rotationally symmetric dots. An obvious feature for tilt angles around 45 is the anti-crossing of the dark and bright states, which in this case happens at about 5 T. The size of this splitting, as obtained from precise modelling shown in the Fig. 3, is dominated by and gives direct access to the in-plane hole g-factor [5], an important parameter for the emerging idea of quantum information processing using long-lived hole spins. This effect is again typically not visible in standard magneto-pl setups in either Faraday or Voigt (90 tilt) geometry, respectively. This technique is adaptable to a host of different nanostructures giving access to wealth of detailed information about the wave functions, the bright and dark spin states, as well as structural information by probing the 3D confinement properties of the respective nanostructure. [1] T. Kehoe, M. Ediger, R. T. Phillips, and M. Hopkinson, Rev. Sci. Instrum (2010) [2] H. W. Van Kesteren, E. C. Cosman, W. A. J. A. Van der Poel, and C. T. Foxon Phys. Rev. B (1990) [3] A. G. Steffan and R. T. Phillips, physica status solidi a (2002); Physica E (2003) [4] R. T. Phillips, A. G. Steffan, S. R. Newton, T. L. Reinecke and R. Kotlyar physica status solidi b (2003) [5] I. Toft and R. T. Phillips, Physical Review B (2007) Fig. 1: Photo of the experimental setup. The positioner stack is mounted in a rotatable cage. The rotator ANR50 is mounted onto the ANPz50. Fig. 2: Photoluminescence data from a single quantum dot in a magnetic field at 45 inclination to the surface. Fig. 3: Model of the anti-crossing data shown in Fig. 2. Emission energy and diamagnetic shift have been subtracted in this model. Fig. 1-3 courtesy of M. Ediger and R. T. Phillips, University of Cambridge. ANPxyz51/LT ANC300/3 linear stepper positioners providing highest stability piezo positioning controller attocube systems AG All rights reserved.

8 APPLICATION NOTE P16 Mechanically controlled multi-contact break junctions Break junctions have been established as one of the most common experimental techniques for the investigation of electrical transport properties on the atomic scale. In most of the setups realized so far, the whole substrate, carrying a thin contact between two leads, was carefully bent by a macroscopic rod. This technique enables a reversible opening and closing of a molecular switch on the atomic level. Although the actual atomic configuration may differ due to local rearrangements from one cycle to the next, the technique very reproducibly shows a clear conductance quantization prior to the transition into the tunneling regime. In this application, Waitz et al. have used a novel approach [1], where small tips with a radius of µm (made from either glass or graphite) were used in combination with thin silicon membranes and precise positioning units to locally stretch the substrate, allowing to individually address multiple break junctions. Samples were produced by a complex process including electron beam lithography and reactive ion etching, yielding free-standing bridges made from either Al, Pt, or Au. After fabrication, samples were placed onto the breaking mechanism, consisting of a chip carrier, a micrometer screw-controlled x-y table and an attocube ANPz100 positioner, see fig. 1. The ANPz100 was used in slip-stick mode for coarse approach, and in scanning mode to adjust the deflection of the membrane with sub-nm precision. The motion of the tip was monitored with an optical profiler with integrated microscope and was recorded by a CCD camera. The measurements nicely show that the displacement of the membrane needed for breaking the nanobridge strongly depends on the lateral position of the tip on the back side of the membrane (see Fig. 2). As expected, the required deflection for breaking a junction increases with increasing distance from the junction. Hereby, larger deflections are required in case of a motion perpendicular to the electrical contacts compared to a motion along the latter. The versatility of the setup was nicely demonstrated by a device containing two junctions placed perpendicular to each other. Fig. 3 shows the time-dependent conductance of both junctions when opening and closing with constant speed for different positions in the x-y plane. When positioning the tip close to junction A, junction B is mainly unaffected and vice versa. Similar configurations could potentially be used for studying charging effects in metallic single-electron transistors with variable junctions. In summary, this experiment demonstrates a novel break-junction setup using thin membranes. The technique overcomes the limitation of previous experiments by allowing to control more than one junction on the same circuit. This technique will be used for studying the influence of optical excitations onto the conductance and for controllable metallic single-electron transistors. [1] R. Waitz, O. Schecker and E. Scheer, Rev. Sci. Instrum. 79, , 2008 (*) Reprinted with permission from R. Waitz, O. Schecker and E. Scheer, Rev. Sci. Instrum. 79, (2008). 2008, American Institute of Physics. Fig. 1: (a) Schematics of the breaking mechanism, showing the sample holder and a cut through the sample (not to scale). The image further depicts the tip, the mechanical x-y positioning stage and attocube s ANPz100 nanopositioner. (b) Zoom into panel (a), demonstrating the working principle of the setup. The typical membrane size is 0.6 x 0.6 mm 2 with a thickness of 340 nm. Fig. 2: Sensitivity of the setup to lateral motion of the tip. The main panel shows the displacement in z-direction required to break a nanobridge as function of the lateral position of the tip. The directions x and y are defined in the inset. Fig. 3: Time-dependent conductance of junctions A and B as depicted in the micrograph to the right. The tip was located at the position indicated by the green cross (the inset was recorded at the position indicated by the circle). At t = 160 s the motion direction of the tip is reversed. Fig. 1-3 courtesy of R. Waitz, O. Schecker and E. Scheer, University of Konstanz, Germany (*). ANPxyz101/LT ANC300/3 linear stepper positioners providing highest stability piezo positioning controller attocube systems AG All rights reserved.

9 nanotooling Probe Stations for extreme Environments APPLICATION NOTE PS01 Cryogenic Probe Station attocpsx4 In a series of tests with the new released attocube systems probe station, Munich researchers have found significant benefits for their research of nano-electro-mechanical structures (NEMS) and related high frequency (HF) experiments. In the basic version, the cryogenic probe station consists of four 3 axes positioning stacks (ANPxyz50/LT) allowing to position four probes independently onto a sample with high precision (max. sample diameter: 6 mm). The positioning can be monitored by a camera system. A picture and schematic drawings of the setup are shown in Fig. 1. The probes can be placed within a center area of 4 x 4 mm 2 even at 4 K. The sample is fixed in the middle and a configurable optic allows imaging the center area. (a) (b) (c) In a first series of tests at the Ludwig-Maximilians-University (LMU) in Munich, the positioning of the probes on the contact pads have proven to be extremly reliable and repeatable. Here, each probe consists of two tips (signal and ground), resulting in four ultra-compact HF probes. A series of more than 100 probe positionings showed identical contact resistance and no damage of the contact pad! The contacting was proven to be a safe and reliable process. Fig. 1: (a) Picture of the cryogenic probe station attocpsx4. (b) Side view showing the overall compact design. (c) Top view with four ANPxyz50 nanopositioning stacks controlling the measurement tips. 0-0,5 Comparison of conventional wire bonding with contacting attocube systems probestation wire bonding probestation Furthermore, a NEMS sample was tested for its HF characteristics. The sample consisted of nano-mechanical freely suspended Si-bars of 150 nm width, 6 µm length and 100 nm thickness with an additional 50 nm thick layer of Au on top. The Au-pads providing the contact had a size of 100 x 100 µm 2. The sample consisted of 20 identical structures, thus allowing for statistical in-situ studies. The results compared to conventional wire bonding are shown in Fig. 2. The measured damping using the attocpsx4 was as low as -2 db at 4 K and 12 T. This is slighly more than achieved with conventional wire bonding. However, while bonded wires tend to vibrate in magnetic fields when a signal is applied (thus showing resonances), the test with the attocube probe station showed absolutely constant, undisturbed contacting. This is a major achievement, the Munich researchers say. The electro-magnetical excitation of the NEMS resonator for different magnetic fields is shown in Fig. 3. One of the major benefits of this probe station is the possibility to address all 20 structures at a temperature of 4 K while the field was engaged with 12 T. This allows comparing structures that have undergone identical processing. The process of warming up the system, renewing bonded wires, reassembly and cooling again was a time consuming and unreliable process in the past. Now, using the attocube probestation, testing of many structures within one cooling cycle at high magnetic fields is enabled. References: Daniel König, LMU Munich, Germany, Daniel.Koenig@physik.uni-muenchen.de Damping [db] Damping [db] 0-0,5-1 -1,5-2 -2, ,5-2 -2,5-3 -3,5 Temperature: 4K Magnetic Field: 12T Frequency (khz) Fig. 2: Comparison of conventional wire bonding with attocube systems probe station attocpsx4. Measurement conditions: 4 K, 12 T. Electromagnetic Excitation of a NEMS-Resonator 2µm Temperature: 4K Excitation Power: -73dBm 12 Tesla 10 Tesla 8 Tesla 6 Tesla 12,78 12,80 12,82 12,84 12,86 12,88 12,90 12,92 12,94 12,96 Frequency [MHz] Fig. 3: Electromagnetic excitation of a NEMS resonator. Insert: SEM-picture of the resonator structure. attocpsx4 ANPxyz50/LT ANC150 cryogenic probe station high precision, piezo electric, inertial positioner electronic controller attocube systems AG All rights reserved.

10 nanotooling Solutions for extreme Environments Vibration measurements on a Janis He flow cryostat equipped with attocube s nanopositioners In this experiment, the vibrometry level of a Janis SuperTran continuous flow cryostat in operation was measured. The cryostat was equipped with two low temperature compatible attocube ANPx101 positioners as shown in Fig. 1 b). The measurements characterize the overall stability of this setup, while operated with liquid He. a) The experiments were done using the easy to use attofpsensor head shown in Fig. 1 a) and an attocube ASC500. A differential method was used: two points were measured and the results were subtracted. The first measurement took place on the cryostat body; whereas the second was done above the sample holder, as shown in Fig. 2. The attofpsensor was attached with double sided tape on the cryostat housing. Aluminium mirrors were used to back-reflect the laser light. The sample holder inside the cryostat was at low temperature of about 9 K during the measurements. No pumping device was attached to the cryostat during the experiment and the positioners have been connected to ground during the measurements. The results of the measurements are given in Fig. 3. Due to the extremely low noise background provided by the use of the attofpsensor, one can clearly observe that at room temperature the cryostat vibrations are lower than 10 pm/ Hz. At low temperature, cooling-generated vibrations with frequencies around 500 Hz are present although these peaks are smaller than 100 pm/ Hz. In summary, vibration measurements on an operating Janis Super- Tran cryostat equipped with two ANPx101/LT positioners have been performed using the attofpsensor. The measurements show that the overall vibrations of such a setup are lower than 100 pm/ Hz at low temperature. These vibrometry measurements have been performed by P.-F. Braun in the attocube application labs. b) Fig. 1: a) attofpsensor head and mount; b) Janis SuperTran cryostat with installed attocube nanopositioners and sample holder. single mode fiber f = 18.4 mm collimator mirror cage plate sample holder ANPx101 ANPx101 vibration isloation mat 2 objective holder mirror O-ring He flow Fig. 2: Schematic of the measurement setup. The numbered red circles show the locations where vibration measurements were obtained. 1 Janis SuperTran attofpsensor ANPx101 /LT Janis Helium Flow Cryostat attocube fiber probe sensor highly stable, low temperature compatible nanopositioners Frequency (Hz) Vibration Displacement (pm/ Hz) K 300K Fig. 3: Vibration of the SuperTran cryostat, measured at 9 and 300 K. attocube systems AG All rights reserved.

11 nanotooling Solutions for extreme Environments APPLICATION NOTE PS03 Compact confocal microscope integrated into the attouhvchamber. Based on the design of the attocube s low temperature compatible attocfm I a confocal microscope setup has been integrated into the attouhvchamber. The tests show superior performance of the optical microscope while enabling an easy optical access for sensitive applications such as Bose-Einstein Condensates, the detailed characterization of waveguides. The measurements have been performed using a standard confocal head together with a special lens setup for the attouhvchamber. The optical beam from the confocal setup was guided into the UHV chamber though an optical broadband window. A laser with a 635 nm wavelength and a UHV compatible objective with the following properties have been used: focal length of 1.56 mm and an NA of 0.68 which results in a theoretical spot size of ~ 600 nm and resolution of at best ~ 450 nm. The confocal head and the objective were stationary, while the sample was mounted on an ANPxyz101 positioner set for coarse alignment in combination with an ANSxy100 scanner for scanning purposes. The sample was a standard chess board structure with ~ 60 nm high SiO 2 structures on Si substrate with 2 µm periodicity. The whole setup was at room temperature and UHV conditions, with the pressure less than 1E-9 mbar. Fig. 1: Image of the chess-board grating with 2 µm periodicity. Red corresponds to high, black to low intensity. From the graph, one can see that the spot is very good circular. In Figure 1 the result of the measurement is shown. The image shows clearly the periodicity of the grating at good contrast. Additionally, the image shows that the circular spot size of the setup has no distortions or aberrations. In summary, it has been shown that the attouhv chamber can be easily combined with the confocal attocfm I setup with no compromises on the quality of the measurement. Fig. 2: Image of the chess-board grating with 2 µm periodicity.??????????????????????????????????????????????????????????????????????????????????????????????????? attouhvchamber attocfm I ANPxyz101/UHV ANC150 miniaturized UHV chamber confocal microscope high precision, piezo electric, inertial positioners electronic controller attocube systems AG All rights reserved.

12 NANOPOSITIONING APPLICATION NOTE P01 attocube systems positioners for PL measurements in high magnetic fields The attocube systems positioners ANPxyz100/LT have been used in a setup for optical measurements in LHe temperature and magnetic fields up to 28 T at the Grenoble High Magnetic Field Laboratory. In the setup laser excitation is delivered using a single-mode fiber and is focused onto the sample with two microlenses. A multimode fiber is used for photoluminescence (PL) collection. The estimated laser spot size was 20 µm and its position over the sample is controlled by an attocube systems ANPxyz100/LT set of piezo-steppers. The setup has been placed in a non-magnetic steel tube of 32 mm diameter and immersed in liquid Helium. The 1.8 m long tube can be mounted in a Helium cryostat. The cryostat can fit in the bore of a resistive magnet in the Grenoble High Magnetic Field Laboratory, which supplies continuous magnetic field up to 28 T. The PL spectra were dispersed by a 1 m double grating monochromator and focused onto a CCD. Both, Ar+ laser and Ti:Sapphire tunable lasers were used for the measurements. A general view of the setup is shown in Fig. 1. One can see the fixed fibers and lenses (middle part of the figure) and the sample, which is mounted onto the set of attocube systems x, y, and z piezostages (right-hand side of the figure). During measurements the setup is immersed in liquid Helium and subject to magnetic fields up to 28 T. Fig.1: General view of the setup. Properties of the setup can be presented in an example measurement of the near-edge photoluminescence of an epitaxial layer of GaAs (see Fig. 2) excited with laser light of 796 nm. A broad PL band around 825 nm is due to the recombination of bound excitons in GaAs. The relatively long wavelength of the excitation light permits its penetration into the bulk GaAs, which results in the seen broadening of the spectrum. Dips in the spectra around 816 nm result from a reabsorption of the light emitted from bulk GaAs by free excitons in the epitaxial layer of GaAs. Its dependence on the actual position on the sample reflects most likely a strain distribution in the epitaxial layer. Fig.2: Scanning photoluminescence spectrum of a bar-like sample of epitaxial GaAs. The setup has also been successfully used for single-dot spectroscopy measurements in high magnetic fields. The number of semiconductor self-assembled quantum dots is limited by mesa-patterning of the sample (submicron sized mesas are used for measurements on a single quantum dot). An example of the obtained results is presented in Fig. 3. A series of emission lines due to recombination of excitons in a single quantum dot can be followed in magnetic fields up to 26 T. A diamagnetic shift as well as the splitting of lines can be seen in the trace of the emission lines versus magnetic field. The emission lines are due to excitons involving the carriers from the ground state ( s -shell) of a single quantum dot. Contact persons: M. Potemski, Grenoble High Magnetic Field Laboratory, Grenoble, France A. Babinski, Warsaw University, Warsaw, Poland C. Bödefeld, attocube systems, Christoph.Boedefeld@attocube.com Related article: Single-Dot Spectroscopy in High Magnetic Fields by A. Babinski, S. Awirothananon, J. Lapointe, Z. Wasilewski, S. Raymond, and M. Potemski, to be published in Physica E. Fig.3: Single-dot spectroscopy of a single quantum dot in high magnetic field of up to 26 T. ANPxyz100/LT ANC150/3 high precision, piezo electric, inertial positioner for big loads electronic controller attocube systems AG, Viktualienmarkt 3, D München, Germany, Tel. +49 (0) , Fax. +49 (0) attocube systems AG All rights reserved.

13 NANOPOSITIONING APPLICATION NOTE P03 Vibrations of the ANPxyz50 Positioning Unit Measured Using the attocfm II (1 Version) The attocfm II confocal microscope is thermally compensated guaranteeing unreached stability required e.g. to perform single quantum dot spectroscopy over a long period of time. Ultra compact versions for 1 bore liquid Helium dewars and larger versions for 2 bore cryostats or similar chambers are available. The 1 version of the attocfm II is equipped with an ANPxyz50 positioning unit. The vibrations of this ANPxyz50 positioning unit can be measured optically by means of confocal microscopy. Having an ideally flat, reflecting sample, the optical signal reaches a maximum when the sample surface lies in the focal plane (Figure 1). By positioning the fiber at half maximum of the signal, a change in Z-position (e.g. vibrations) will change the intensity of the measured reflected light significantly, thus providing information on the system s vibrations. The vibration spectrum of the confocal microscope attocfm II (1 version), which is composed from an ANPxyz50 positioning unit, was recorded at room temperature. The spectrum of the noise is is shown in Figure 2. Vibration amplitudes of less than 100 pm were observed, main. The total vibration (integral of all harmonics) was determined to be about 800 pm. The image depicted in Figure 3 has been recorded with the confocal microscope attocfm II (1 version) in scan mode at a wavelength of 633 nm. The sample was a SiO 2 on Si chess board with a period of 2 microns. The scan range was 15 x 15 microns. Fig. 1: Graph of the collected intensity as a function of the Z axis position in the confocal set-up. By changing the position of the plan of focus on the sample, the measured intensity first increases and then decreases again. Fig. 2: Vibration spectrum of the ANPxyz50 positioning unit recorded at 300 K. The attocfm II (1 version). Fig. 3: Picture of the chess board using the CFM II 1. The scan range is 15 microns using only 45 Volts. ANPxyz50 attocfm II ANC150/3 ANC200 attoscan attoview high precision, piezo electric, inertial positioner for 1 setups highly stable confocal microscope for 1 setups electronic controller electronic scan controller data acquisition software data viewing and editing software attocube systems AG, Viktualienmarkt 3, D München, Germany, Tel. +49 (0) , Fax. +49 (0) attocube systems AG All rights reserved.

14 NANOPOSITIONING APPLICATION NOTE P04 Vibrations of the ANPxyz100 Positioning Unit Measured with an Interferometric Setup The force detection scheme attocube systems uses for scanning nearfield optical microscopy (SNOM), atomic force microscopy (AFM) applications or vibration measurements of a positioning unit is based on an all fiber low-coherence interferometer (Figure 1). A laser diode (SLD source ) beam coupled into a single mode fiber is used to illuminate a Michelson interferometer based on a 50/50% fiber coupler. At the end of the second interferometer arm 4% of the light is reflected at the glassair interface. 96% of the light is transmitted and partially reflected at the cantilever or vibrating unit. The distance d between the cantilever or vibration unit and the end interface of the control fiber is typically 20 microns. Therefore, the tip interface or the surface of the vibrating unit and the fiber end face form a Fabry-Perot interferometer of low finesse. Monitoring the intensity of the interference fringes allows measuring the vibration amplitude. The low coherence of the SLD source has the advantage to eliminate spurious interference signals resulting from other reflections in the set-up (e.g., the coupler), thus leading to an increase of the signal-to-noise ratio of about 30 db. The excitation is supplied by a digital lock-in amplifier. The measured optical interference signal can be amplified by the lock-in amplifier. The precision of the vibration amplitude measurement is 160 fm/hz 1/2. Figure 2 illustrates schematically the interference signal measured with the system described above. By positioning the fiber at half maximum of the signal, a change in distance will change the signal significantly. Fig. 1: Schematic representation of the interferometric setup. R1 (=4%) and R2 (=96%) are the reflection coefficients at the end of the control fiber and the vibration unit. This simple setup allows to measure the vibrations of the ANPxyz100 in the Z direction. The vibration spectrum recorded at room temperature is illustrated in Figure 3. The main vibrations observed around 600 Hz were determined to be always smaller than 20 pm. In the DC regime (if the noise is integrated over the entire spectrum), the noise is always smaller than 33 pm! Fig. 2: Schematic drawing of the interference signal. This ultra-high stability of the ANPxyz100 positioners permits atomic resolution in scanning probe microscopy applications. The ANPxyz100 positioning unit. Fig. 3: Spectrum of the vibrations of the ANPxyz100 positioning unit recorded at 300 K. ANPxyz100 ANC150/3 fiber based iterferometric set-up high precision, piezo electric, inertial positioner electronic controller attocube systems AG, Viktualienmarkt 3, D München, Germany, Tel. +49 (0) , Fax. +49 (0) attocube systems AG All rights reserved.

15 Ultra-compact xyz Fiberoptics Positioning System The precise alignment of optical elements in a Micro-Opto-Electro- Mechanical System (MOEMS) is of uttermost relevance in order to realize reliable set-ups. Thereby, the application of ultra-compact elements enables on one side the accurate positioning of optical elements such as fibers or optical detectors and on the other side the manufacturing of low loss systems. As a consequence to the increasing requirements in the electro-optics industry, piezoelectric fine adjustment systems have significantly gained in importance as they provide extremely high resolution, responsiveness, and mechanical controllability. Due their highly successful application as nanopositioning tools in extreme environments the attocube systems positioner can nowadays also be used for precision positioning of optical components. Their ultra-compact size (see Fig. 1) and a modular set-up design thereby allow flexible and universal applications. Fig. 1: The ultra-compact ANP100 xyz attocube positioners The working mechanism of the attocube systems positioner relies on the so called slip-stick principle. Via a fast acceleration of a guided rod over a short period of time the movable part of the positioner (sliding block) remains nearly non-displaced due to the overcome of friction. If in a subsequent step the guiding rod moves back to its initial position slowly enough the movable part of the positioner sticks to it and thus performs a net step. Hence, this slip-stick translation stage enables reliable and controllable motion of the sliding block over millimeter ranges with small and reproduceable steps. The product key features for a fiberoptics positioning system (see Fig. 2) are as follows: > Overall size of the positioners: 24x24x53 mm (+ travel) > Travel distance: 7x7x6 mm with step sizes down to 50 nm > Scan area: 9x9x9 µm (sub-nm resolution) If a scan area of 9x9x9 µm is not sufficient an optional setup can perform fast and high precision scanning in an area of 40x40x24 µm with sub-nm resolution by using a piezo electric xyz-scanner (ANSxyz100) on top of the described set-up. Custom designed software enables the automatization of e.g. a fiber alignment process by controlling the piezo electric positioning unit via a feed-back loop. Furthermore, the attocube systems positioners can be operated in extreme working environments such as ultra-low temperature, ultra high vacuum, and high magnetic fields. ANPx100 ANPx100 ANPz100 Fig. 2: Schematic of a Fiberoptics Positioning System using an ANPxyz100 positioning unit x y z EXAMPLE APPLICATIONS > Micro- and Nanopositioning > Laser Scanning > Mirror Shifting > Fiber Alignment > Laser Coupling > Detector Alignment ANPx100 high precision, piezo electric, inertial positioner ANPz100 high precision, piezo electric, inertial positioner ANSxyz100 high precision, piezo electric xyz-scanner for high precision 3D scanning ANC150/3 piezo step controller ANC200/3 piezo scan controller attocube systems AG All rights reserved.

16 NANOPOSITIONING APPLICATION NOTE P06 Atomic Resolution Imaging in STM using attocube Positioners Since its invention (1983) and Nobel prize (1986), Scanning Tunneling Microscopy (STM) and related Scanning Probe Microscopies have become some of the most important new laboratory techniques for studying sub-nanoscale surface phenomena. STM works by scanning a sharp conductive tip over a surface. A bias voltage is applied between the tip and a conductive sample. When the sample is approached within a few Å from the tip, a tunneling current can be established indicating the proximity of the tip to the sample with very high accuracy. Most of the tunneling current can flow through a single protruding atom on the tip and sub-å resolution in z can be achieved on a clean surface with a sharp tip. There are two different modes in STM: In constant height mode, the tip is moved only in plane. Thus, the current between the tip and the sample surface visualizes the sample relief. In this mode, adjustment of the surface height is not required and a higher scan speed can be obtained. Anyway, constant height mode is only applicable if the sample surface is very flat, because surface corrugations higher than 5-10 Å will cause the tip to crash. In this case, maintaining a constant tunneling current by adjusting the height with a piezo element and monitoring the piezo voltage while scanning, allows to image the surface. This mode is called constant current mode (see Fig. 1). I z Tip Scan x Sample Fig. 1: Schematic illustration of the constant current mode. Fig. 2: The ultra-stable ANPz100. STM gives true atomic resolution on selected samples even at ambient conditions. This technology can be applied to study conductive surfaces or thin nonconductive films and small objects deposited on conductive substrates. Dr. Amakusa (JEOL, Japan) is currently building a STM operating at low temperatures and high vacuum conditions. The scan head has been fabricated using attocube system s ANPz100 (Fig. 2) for the tip approach. This ultra-stable linear positioner provides atomic resolution over a travel range of 6 mm. The image shown in Fig. 3 was acquired at room temperature and high vacuum conditions (2 x 10-8 mbar) on a Si(111) surface in constant current mode (tunneling current: 0.2 na, bias voltage 2.0 V, scan range 38 nm x 38 nm). Atomic resolution can be achieved! Reference: (1) The data was generously provided by Mr. Amakusa, JEOL, Japan and Dr. Hosoi, Hokkaido University, Japan. Fig. 3: Atomic resolution image of a Si(111) surface recorded at room temperature and high vacuum conditions. The scan area was 38 nm x 38 nm. Image by courtesy of Mr. Amakusa, JEOL, Japan and Dr. Hosoi, Hokkaido University, Japan. ANPz100 ANC150 high precision, piezo electric, inertial positioner electronic controller attocube systems AG, Königinstrasse 11 A (RGB), D München, Germany, Tel. +49 (0) , Fax. +49 (0) attocube systems AG All rights reserved.