Facilities

PREM Facilities

Materials Characterization

Integrated Scanning Probe – Optical microscopy system

This system integrates a versatile AIST scanning probe microscope with a high resolution Horiba optical micro-spectroscopy system.  Setup, data collection and data analysis for both optical and scanning probe microscopies are handled within a single software environment.  The scanning probe microscope is routinely used for a variety of measurements, including:

  • Topography: contact, semi-contact, and intermittent contact atomic force microscopy (AFM), scanning tunneling microscopy (STM)
  • Electrical characterization: Kelvin probe (amplitude- and frequency – modulated), conductive AFM, electrostatic force microscopy, scanning capacitance microscopy, STM
  • Magnetic characterization: Magnetic force microscopy
  • Optical characterization: Tip-enhanced spectroscopy, scanning near field microscopy using aperture fiber probes.

The system is designed for operation with a Horiba LabRam HR optical spectroscopy system, with a scan head that allows optical access through high numerical aperture objectives from the top and side and a 1300 nm feedback laser that will not interfere with most optical measurements.

The Horiba LabRAM HR evolution Raman microscope system provides optical measurements with excellent spatial and spectral resolution, and high sensitivity.  Four excitation lasers (473 nm, 532 nm, 633 nm and 785 nm) enable selective excitation of specific samples, or avoidance of fluorescence for Raman spectroscopy.  Notch filters allow measurement of Raman spectra less than 150 cm-1 from the excitation line using the 473 nm, 532 nm and 785 nm lasers.  Measurements to 10 cm-1 are possible with the 633 nm laser.  An electron multiplying CCD camera allows detection of extremely weak signals with short integration times, and enables rapid mapping with sub-micron lateral spatial resolution.

Training:  B. Chitara (bchitara@nccu.edu); Reservations:  Lab Agenda website.

Scanning electron microscope system

SEM

This FEI NanoSEM 630 thermal field emission scanning electron microscope (SEM) is capable of achieving 1 nm resolution for secondary electron imaging, and less than 1 nm for transmission electron imaging. This instrument has a low vacuum (up to 1.2 torr) operation mode that allows imaging of samples that are not electrically conductive without carbon or metal coating.  Imaging at low acceleration voltages to highlight surface features or minimize sample damage can be performed with a high contrast, low voltage detector or beam deceleration.   The SEM is integrated with an energy dispersive x-ray spectroscopy system for elemental analysis, and an electron diffraction system for determination of crystal structure and orientation.   Both of these systems can be used to map materials properties with spatial resolutions well below 100 nm.

Training: M. Wu (mwu@nccu.edu); Reservations: Lab Agenda website.

Ultrafast Optical Spectroscopy

Transient absorption and photoluminescence lifetime microscopy measurements are performed using an inverted confocal microscope platform that allows focusing of beams from above and / or below the sample with 100x, 1.4 NA oil immersion objectives.  Samples are mounted on a high resolution closed loop piezoelectric xyz translation stage with nanometer scale repeatability, and the excitation beam can be scanned using an xy galvanometer that enables independent control of excitation and probe locations.  Ultrafast excitation pulses are provided by an optical parametric amplifier pumped by a Ti:Al2O3 laser system.  For transient absorption measurements, broadband pump probe measurements can be performed using a supercontinuum probe, an EMCCD camera attached to a grating spectrometer, and a 200 mm mechanical delay stage.  Time resolved photoluminescence is performed using time correlated single photon counting.  This system is capable of sub-micron spatial resolution and time resolutions of < 150 fs for transient absorption and < 50 ps for photoluminescence lifetime mapping.

Contact M. Wu (mwu@nccu.edu) if you are interested in using this system.

Time resolved millimeter wave photoconductivity system

This system is based on time resolved changes in the transmission or reflection of a continuous wave millimeter-wave beam after photoexcitation by an ultrafast laser pulse.  This technique can be used to determine carrier mobilities and time-dependent populations without deposition of electrical contacts.  The millimeter wave probe can be tuned from 110 GHz to 170 GHz, and the primary excitation source is a frequency doubled Nd:YAG laser with a ~ 350 ps pulse width.  The time resolution of the system is currently limited by the laser pulse width to ~ 250 ps (using deconvolution techniques).

Contact M. Wu (mwu@nccu.edu) if you are interested in using this system.

Materials Growth

Hot Wall CVD Systems

These systems are built around tube furnaces capable of reaching 1100ºC.  The systems are evacuated by dry scroll pumps and can reach a base pressures of < 5 x 10-3 torr.  Three mass flow controllers are available to control gas flow in each system, and pressures are automatically controlled by downstream throttle valves connected to capacitance manometers.  Substrates and / or source materials for thermal evaporation can be transported into and out of the heated zones while the system is under vacuum using magnetically coupled carrier tubes to avoid uncontrolled growth during furnace heating and cooling periods.  One system is dedicated for graphene growth, and one system is dedicated to growth of inorganic semiconductor nanowires.

Contact M. Wu (mwu@nccu.edu) or B. Chitara (bchitara@nccu.edu) if you are interested in using these systems.

UHV Deposition System

This UHV system has a base pressure < 1 x 10-9 torr and is used for growth of nanostructures and thin films via pulsed laser deposition and electron beam evaporation.  For pulsed laser deposition experiments, the chamber contains a six target carousel and a heated, three axis substrate translation stage.   Both the target and substrate mounts are capable of motorized rotation to allow deposition of large areas with high uniformity. The laser pulse can also be raster scanned over the surface by a motorized mirror to avoid digging circular trenches due to target rotation alone. The chamber also houses a three crucible 25kW electron beam evaporation system that is used to deposit dielectric and metallic thin films.  This system has a magnetic XY beam sweeping capability to increase film uniformities.  Substrates can be transferred into and out of the main deposition chamber through a load lock without breaking vacuum.

Contact M. Wu (mwu@nccu.edu) if you are interested in using this system.

Material Processing

Cleanroom

The class 1000 cleanroom contains the following equipment for electron beam lithography and thin film characterization:  Suss MJB3 mask aligner, Laurell spin coater, ultrasound, two chemical fume hoods, cleanroom oven, a plasma cleaner and a thin film characterization (n and k) system used to determine thicknesses of spin coated films.