Bruker Corporation and Oxford Instruments have jointly announced the integration of Oxford Instruments’ Optistat™Dry Cryofree® cryostat with Bruker’s Vertex series of FTIR research spectrometers. This article outlines the capability of the combination of OptistatDry and Vertex systems that can be used in various spectroscopy experiments.
Sometimes the cost and availability of liquid helium can be a factor in choosing a cryogenic system for low temperature analysis. These concerns can be addressed with a closed-cycle cryogenic system as an alternative. The OptistatDry uses a mechanical cooler. However, due to the mechanical interface design, interference caused by vibration has been reduced to levels that cannot be detected in the spectral regions of interest.
The OptistatDry cryostat has been combined and fully incorporated with Bruker’s Vertex series of FTIR spectrometers. It can be utilized for material characterization without the need for liquid helium. It is very easy to use and samples can be changed without modifying the alignment. The cool down time is approximately 160 minutes.
The OptistatDry has been customized for use with the Vertex series of spectrometers, including the purged V80 and V70 (Figure 1), and the V70v and V80v vacuum systems. It is directly mounted to the V70 spectrometer utilizing Bruker’s proprietary quicklock baseplate.
The cryostat is fully integrated in such a way that temperature and data collection control is synchronized and can be performed easily via Bruker’s OPUS software (Figure 2). Users can easily setup temperature ramps so that data can be readily obtained during decreasing and increasing temperature ramps. Data analysis is greatly facilitated because the acquired data has the associated temperature which is stored automatically.
Figure 1. OptistatDry mounted in a Bruker V70 FTIR spectrometer
Figure 2. Screen capture of the temperature control user interface in Bruker’s OPUS software (optional O/PRO package).
The Bruker VertexFM infrared spectrometer is capable of covering the entire spectral range, from 30 wavenumbers to 6,000 cm-1 in a single scan. A bolometer is suitable for performing measurements in the far infrared (FIR) region, as it has much greater sensitivity compared to a DTGS detector.
However, the DTGS detector can be used for studying a large number of samples, thanks to the high sensitivity of the Vertex FTIR spectrometers. This is especially attractive in utilizing the VertexFM configuration, which features a DTGS detector with a diamond window to cover the NIR-FIR spectral range.
Users can configure the OptistatDry with optical windows that are suited for the spectral range of interest. As the sample chamber is readily accessible, the windows can be easily exchanged.
Application Example – Boron in GaAs
The combination of OptistatDry and Vertex can be used in a wide variety of applications, ranging from matrix isolation, to semiconductor materials characterization, to low temperature photoluminescence investigations, and quantum dot research. Figure 3 displays the single channel spectra of the background (top) and the 1.21 mm thick GaAs sample (bottom) collected with the OptistatDry and Vertex 70 with the region of interest circled.
Figure 3. Single channel spectra of the OptistatDry/Vertex70 system background (top) and the GaAs sample (bottom).
With 3 mm polyethylene windows mounted on the OptistatDry, the data was collected at 4 cm- 1. The Boron-10 isotope can be easily observed in Figure 4, which shows significant shifting of the isotope as a function of temperature. The system delivered high-quality data even though the polyethylene windows and GaAs sample are strongly absorbing in the region of interest, demonstrating its excellent sensitivity.
Figure 4. The absorbance spectra of the Boron-11 isotope in GaAs as a function of temperature.
Conclusion and Outlook
The OptistatDry and the Vertex are systems that can be upgraded as the research needs change. Oxford Instruments Nanoscience's OptistatDry is designed with a modular philosophy that enables the cryostat to evolve – start with a basic system and as research needs change, upgrade to additional functionality.
For example, it is possible to add extra wiring, different sample holders, and windows at a later date. The Vertex FTIR systems are designed to be readily upgraded to incorporate other spectral ranges, FT/Raman capability, IR microscopy, step-scan that is useful for photoluminescence work, and much more.
This information has been sourced, reviewed and adapted from materials provided by Oxford Instruments Nanoscience.
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