UEM and LASER Systems
***Contact Dave via email to discuss potential collaborations and use of the UEM instrument at Minnesota.***
- FEI Tecnai Femto UEM: The UEM is based on FEI's Tecnai G2 T20 200 kV platform with TWIN objective lens assembly. The detector is a Gatan OneView camera with 4096 x 4096 active pixels at 15 micrometers each.
- Specimen Holders: Single-tilt single- and multi-specimen holders (FEI), double-tilt holder (FEI), rotation holder (FEI), and double-tilt liquid nitrogen holder with Faraday cup (Gatan 636). In addition to these, which belong to the UEM group, there are a variety of other holders available for use on campus (e.g., heating and cryo-holders, etc.).
- Light Conversion PHAROS Femtosecond LASER: Diode-pumped solid-state oscillator with chirped-pulse amplifier and stretcher/compressor modules. Pulse duration of 220 fs FWHM with capability to stretch to 10 ps. Variable repetition rate (single-shot to 1 MHz) with additional pulse picker for external triggering. Lasing material is Yb:KGW with 1,030 nm fundamental output. Power is greater than 6 W above 30 kHz with 200 microjoules per pulse below. A custom Light Conversion HIRO harmonics generation module is used for SH and TH generation. Emission of the fundamental and harmonics from the HIRO are simultaneous and collinear, and optics are available for optimized conversion at several different repetition rates. The FH is generated on the table outside the HIRO box.
- Bright Solutions WEDGE HF Nanosecond LASER: Nd:YAG Q-switched diode-pumped solid-state LASER. Pulse duration of 700 ps to 3 ns. Pulse energy at 1,064 nm is 180 microjoules (10 kHz). The SH and FH are generated on the table.
- Aerotech Linear Motor Translation Stage: 1 meter of travel with granite base plate for increased flatness. HALAR linear error correction calibration at height of Newport broadband retroreflector. Aerotech SOLOIST controller enables travel below one micrometer with reversibility of 250 nm.
- Newport Optical Table: The LASER systems, stage, and optics are mounted on a Newport research-grade optical table with four-point tuned damping. Table dimensions are 4' x 8' x 24". A custom Newport breadboard is used for delivering light to the UEM periscopes.
- LASER Diagnostics and Control: We use a variety of tools for quantification and control, including (i) beam profilers, (ii) power meters, (iii) beam shutters, (iv) IR viewers, (v) oscilloscopes (300 MHz and 1 GHz), (vi) pulse and delay generators, (vii) photo-detectors, and (viii) a GECO scanning autocorrelator from Light Conversion.
- Optics and Optomechanics: We employ a large number and wide range of optics, mounts, and posts consisting of precision-ground stainless steel pedestal posts and low-drift mirror mounts.
Lab and Office Space
UEM Lab Space: The Flannigan Group UEM is housed in the sub-basement (2 floors underground) of the Gore Annex of Amundson Hall on the East Bank of the University of Minnesota-Twin Cities campus. The UEM and LASER systems rest on a 224-square foot vibration isolation slab that is entirely decoupled from the building. The isolation slab is 3-ft thick (50 tons) and rests on a thin layer of sand and an additional 7-ft thick cement column. The room walls and drop ceiling panels are constructed from sound-deadening material rated better than cinder block. The drop-ceiling lattice is suspended from wire, each of which contains a rubber elastomer for reducing vibration transmission to the room. The walls are covered with thick acoustic panels for reduction of reverberation, and moveable acoustic/LASER curtains divide the room into quadrants while not restricting air flow. The air supplies contain HEPA filters rated to ISO 5 (clean room class 100) and diffusers to regulate the air flow velocity to below 5 meters/minute. The room temperature is stable to better than one-tenth of one degree (24 hrs.). Room lighting is comprised of continuously-dimmable LEDs to avoid filament noise and minimize heat load. All service equipment (e.g., chillers, compressors, etc.) is housed in a separate utility chase with the single feed through sealed with acoustic foam. Power and grounding for the microscope are isolated from other sources to minimize electronic noise. The images and accompanying FFTs below demonstrate that the spatial resolution limits of the instrument can be readily achieved in this lab space.
Left panel: BF image of Au nanoparticles showing 2.3 angstrom lattice fringes. Left-center panel: FFT of the image in the Left panel. Right-center panel: DF image of oriented Au showing 1.4 angstrom lattice fringes. Right panel: FFT of the image in the Right-center panel.
Specimen Prep and Analysis
We have a wide variety of equipment and software for specimen prep and analysis, including:
- Allied Multiprep Specimen Polisher: Provides precise micrometer controlled polishing with a great variety of polishing grits. Fine control of the sample stage orientation in combination with polishing pad rotation allows for rapid semiautomatic polishing of hard material samples in various geometries, including plates and wedges.
- Metallurgical Microscope: Dark-field and polarization imaging at magnifications up to 2,500X with dual halogen light sources for operation in reflection and transmission modes. Standard optical microscopes capable of magnifications up to 225X are also available for more routine tasks (e.g., Wehnelt maintenance). All optical microscopes are equipped with digital video cameras.
- UV-Vis Spectrophotometer: Shimadzu UV-1800 dual-beam spectrophotometer. The scanning UV-Vis covers 190 to 1,100 nm and features a 1 nm slit width, thin film holder, five-degree specular reflectance module, and film thickness software.
- Water Purification System: Barnstead MicroPure UV/UF-ST water purification system equipped with ultra-filtration and UV photo-oxidation capabilities.
- Software: Crystal Maker and Single Crystal; COMSOL Multiphysics with various modules.
- Other Notable Equipment: Custom-built workstation for image simulation, automated analysis of massive data sets, and calculations; desktop workstations for each group member; analytical balances; vacuum ovens; split tube furnaces; ultrasonic baths; desktop spin coaters; plasma cleaners; disc punches; two-port mini glovebox; ceramic hot/stirring plates; tools and tool cases.
In addition to equipment available exclusively in the Flannigan Lab, group members have unfettered access to and make heavy use of all equipment at the University of Minnesota Characterization Facility and the Minnesota Nano Center.
