INDIAN INSTITUTE OF TECHNOLOGY BOMBAY

Transcription

1 IIT Bombay requests quotations for a high frequency conducting-atomic Force Microscope (c-afm) instrument to be set up as a Central Facility for a wide range of experimental requirements. The instrument must have a robust design as it will be used daily by students of all levels of experience. A major fraction of the usage will be related to imaging and conductance measurements on thin film substrates and advanced nanoscale devices. As this will be a shared facility instrument, an upgrade path for additional advanced modes, heated chuck, etc is preferred. The high frequency c-afm must meet all of the requirements listed below: Atomic Force Microscope 1. Operating Modes and Environmental Controls The AFM system must be able to image samples and perform measurements in air and in liquid using the same cantilever holder. The cantilever holder must be compatible with most commercial cantilevers. The AFM system must include the following modes: Scanning modes: Contact, AC (tapping), Multi-frequency (able to drive and detect the cantilever motion at more than one frequency simultaneously), frequency modulation (FM), force modulation, electric force microscopy (EFM), magnetic force (MFM), Kelvin Probe (SKPM), Conducting AFM (CAFM), and Piezoresponse Force Microscopy (PFM) Point measurement modes:nanolithography and Nanomanipulation, Force vs Displacement (single point and mapping), IV measurements, and pulse measurements. Conductive AFM The system must allow measurement of current flowing through the sample in the scanning mode, at user-programmable locations and at applied bias voltages.

2 It must be possible to apply complex voltage wave forms such as square, sine, triangle, pulse, or other arbitrary user defined shapes, while concurrently monitoring the current flow through the tip. For DC measurements, it must be possible to sense currents as low as 1pA. It must be possible to apply voltage pulses with rise times, hold times and fall times, all between 5 and 15 ns to the tip and measure current flowing through the tip during the pulse. It should be possible to measure low currents flowing through the sample, at least 10µA or lower, concurrently while the tip is in contact with the sample and a voltage pulse or waveform is applied. It must be possible to apply bias voltages to the sample in the range of -10V to +10V It must be possible to apply an AC bias/signal either to the tip or the sample through software control. The software must provide easy analysis and plotting so that I-V curves can be visualized during measurement in a straight-forward manner. It must be possible to obtain conductivity maps of the sample, which could be overlaid with topographic or imaging maps, in real-time. 2. AFM Scanner and Optical Lever Detection Systems Instrument Resolution It must be possible to obtain atomic lattice resolution in AC mode and contact mode imaging. The same scanner should also be capable of imaging large areas: at least 50µm 50µm 10 µm. Scanner

3 A single closed-loop scanning system with XY range of at least 50 µm and Z range of at least 10 µm is required. The XY scanner must be separate from the Z scanner. In order to conduct tip based measurements, sample scanning must be possible. It should be possible to accept samples up to 50mm lateral dimensions and at least 10mm thickness. The noise in the X and Y sensors must be less than 100pm ADev in a 0.1Hz to 1kHz bandwidth. Z sensor noise must be less than 500pm ADev in a 0.1Hz to 1kHz bandwidth, with sensor nonlinearity <0.1% at full scan. Optical Lever Arm: Light Source and Photodetector The cantilever holder and the optical lever assembly (laser, optics, and detector) must move together on a single rigid frame to eliminate relative motion between components which leads to errors and artifacts during imaging. The optical lever arm must use a low coherence light source (such as an SLD) to reduce artifacts from optical interference effects. The instrument must use an infrared SLD (or equivalent) for the optical lever arm to eliminate optical crosstalk. The SLD (or equivalent) must preferably be incident on the cantilever at an angle (20-25 degrees) to the sample normal to reduce interference and minimize noise. The instrument s DC Detector Noise must be less than 50pm ADev in a 0.1Hz to 1kHz BW. DC Height Noise (deflection noise with the tip on the surface and the gains turned off) must be less than 50pm ADev in a 0.1Hz to 1kHz bandwidth.

4 The photodetector must have an optical sensing bandwidth of at least DC to 1 MHz. 3. AFM Control System Electronics All the control must be 100% digital operation. The sensing bandwidth of the controller must be at least 1 MHz. The overall thermal tunes of the cantilever must be up to at least 1 MHz. There should be BNC access to all major input and output signals from the electronic controller. The AFM instrument must include auto-configuration of external hardware and accessories (ie. plug and play). The instrument must include a user programmable control knob that can be used to fine tune and adjust all scan parameters during any advanced operation. Software The system software must be based in Windows or Linux for compatibility with university network and other laboratory instrument software systems. The software must be capable of driving the cantilever simultaneously at two or more arbitrarily chosen excitation frequencies in AC (dynamic) mode, while simultaneously collecting and displaying the amplitude and phase signals and images from each of these frequencies, along with the height or Z-sensor data. All software must be in open-source software programming language so that users can easily add their control and measurement programs. The system software must include a macro building graphical user interface to automate complete multiple-step experiments and data processing sequences.

5 The system s software must support one-click configuration for most standard measurements. It must be possible to render imaged surfaces in 3D in real-time, during imaging. The AFM control software must include optical image navigation using any realtime optical input. The software must have an image overlay function to combine AFM images with optical images or other plots (such as conductivity maps) for direct feature comparison. The software must allow image files to be exported in standard formats as JPEG, PNG, BMP and TIFF. Must include built-in nanolithography and nanomanipulation software. Must include drift compensation software so that a region of interest can be tracked in real time (<5 nm precision) thereby eliminating any distortion in the image. Drift compensation should be possible during any advanced characterization mode (imaging, pulsed measurement, etc). Must include free offline software for analysis of experimental data. The software must be compatible with PC and Mac for offline image processing. Free software upgrades must be available for the life of the instrument. System Computer The System must include a current commercial computer model suitable for controlling the AFM system and performing data analysis simultaneously. Dual monitors at least 20 must be included. The Computer-to-Controller communication must be via USB2 for easy upgrades.

6 4. Instrument Environmental Isolation The system must include a thermally- and acoustically-isolating enclosure. The enclosure must provide at least 20dB of acoustic isolation. An air temperature control system should be optionally available for the acoustic hood to minimize thermal drift. The system must include an active vibration isolation table. 6. Guarantee, Warranty, Support and Service Must include at least three (3) year warranty on all parts and labor. Must include free AFM software upgrades for the life of the instrument. Must provide biannual training sessions for students during the warranty period.