CRYOFREE

Application note

Applications of the Oxford Instruments’ OptistatDry cryostat
with the Vertex series of FTIR research systems

Introduction
Oxford Instruments and Bruker Corporation jointly announce
the integration of Oxford Instruments’ OptistatTMDryCryofree® cryostat with Bruker’s Vertex series of FTIR
research spectrometers. This application note describes thecapability of the OptistatDry and Vertex combination, thatcan be applied to a wide range of spectroscopy experiments.

Background
Sometimes the availability and cost of liquid helium can be a factor in selecting acryogenic system for low temperature investigations. To address these concerns,
a closed-cycle cryogenic system is an excellent alternative. OptistatDry uses
a mechanical cooler. However, due to the design of the mechanical interface,interference due to vibration has been reduced to levels not detectable in thespectral regions of interest. The OptistatDry has been coupled and fully integrated
with Bruker’s Vertex series of FTIR spectrometers. The cryostat can be utilised forcharacterising materials without the use of liquid helium. It is very easy to use,
where samples can be changed without altering the alignment, the cool down time
is approximately 160 minutes. The OptistatDry has been adapted for use with theVertex series of spectrometers, including the purged V70 and V80 (see Figure 1), as
well as to the vacuum systems, V70v and V80v. The OptistatDry is mounted directly
to the V70 utilising Bruker’s proprietary quicklock baseplate.

Figure 1. OptistatDry mounted in aBruker V70 FTIR spectrometer.

The OptistatDry has been fully integrated such that the control of temperatureand data collection is synchronised and easily performed via Bruker’s OPUS software(Figure 2). Temperature ramps are easily setup such that data can be readily collectedduring increasing and decreasing temperature ramps. Since the acquired data has
the associated temperature automatically stored, data analysis is greatly facilitated.
The Bruker VertexFM infrared spectrometer can cover the full spectral range, from
30 wavenumbers to 6,000 cm-1 in a single scan. While a bolometer is ideal for
conducting measurements in the far infrared (FIR), due to it having much greater
sensitivity than a DTGS detector, most samples can be analysed with a DTGS detector
due to the high sensitivity of the Vertex FTIR spectrometers. This is particularly
attractive in utilising the VertexFM configuration that has a DTGS detector witha diamond window to cover the NIR-FIR spectral range. The OptistatDry can beconfigured with optical windows suitable for the spectral range of interest. Thewindows can be easiily exchanged as the sample chamber is readily accessible.

Figure 2. Screen capture of thetemperature control user interface
in Bruker’s OPUS software(optional O/PRO package).

CRYOFREE

Application noteApplication example – Boron in GaAs
There are a wide range of applications where theOptistatDry and Vertex combination can be applied.
These applications range from low temperature
photoluminescence investigations to quantum dot
research, to matrix isolation, and semiconductormaterials characterisation. Figure 3 shows the single
channel spectra of the background (top) and the1.21 mm thick GaAs sample (bottom) collected with
the OptistatDry and Vertex 70 with the region ofinterest circled. The data was collected at 4 cm-1
with 3 mm polyethylene windows mounted on
the OptistatDry. The data collection time was fiveminutes. The Boron-10 isotope is easily observed
and shifts significantly as a function of temperature
as observed and shown in Figure 4. The excellent
sensitivity of the system is demonstrated by the factthat high quality data was collected even though
the polyethylene windows and GaAs sample arestrongly absorbing in the region of interest.

Figure 3. Single channel spectra of the OptistatDry/Vertex70
system background (top) and the GaAs sample (bottom).

Conclusion and outlook
Both the OptistatDry and Vertex are systems
that can grow as the research needs change.
OptistatDry is designed with a modular
philosophy that allows the cryostat to evolve –start with a basic system and as experimental
needs change, upgrade to additional
functionality. For example, extra wiring, different
sample holders, and windows can be added at alater date. The Vertex FTIR systems can also bereadily upgraded to include other spectral ranges,
step-scan (useful for photoluminescence work),
IR microscopy, FT/Raman capability, and more.

Figure 4. The absorbance spectra of the Boron-11 isotope
in GaAs as a function of temperature.

Contact us at:Authors:

Oxford Instruments NanoScience

Tom Tague, Ph.D., Applications Manager, FTIR/Raman Products, Bruker Corporation, USAnanoscience@oxinst.com

Mark Jackson, Territory Sales Manager, Oxford Instruments NanoScience, USA

www.oxford-instruments.com/nanoscience

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October 2016, Issue 1