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1. Near-ultraviolet Raman and micro-Raman analysis of electronic materials

   https://doi.org/10.1063/1.5054660  

   Nazari, Mohammad; Holtz, Mark W. (December 2018, Applied Physics Reviews)
2. Raman scattering applied to human breath analysis

   https://doi.org/10.1016/j.trac.2024.117791  

   Arachchige, Charuka Muktha; Muller, Andreas (August 2024, TrAC Trends in Analytical Chemistry)

   The chemical composition of exhaled human breath can be strongly correlated to medical conditions such as lung cancer or gastrointestinal diseases. To establish these correlations and, most importantly, to use them in diagnostics, chemical gas detection needs to be performed at trace concentrations, typically at parts-per-million (ppm) levels or below, for many compounds simultaneously. Traditional methods such as gas chromatography, a workhorse in scientific laboratories, is ill-suited for the fast, inexpensive point-of-care diagnostics that would be needed to build statistically-meaningful ensembles over large populations. With the increasing availability and decreasing cost of high power diode lasers and of uncooled CMOS cameras, spontaneous Raman spectroscopy (SRS), a vibrational molecular fingerprinting tool, is emerging as an economic alternative. Although gas SRS scattering cross sections are only on the order of 10$$^{-31}$$ cm$^2$/sr, considerable progress in the development of enhancement techniques has been made over the past decade. The purpose of this work is to review SRS enhancement approaches in the context of established human breath tests, and to provide a comparison with alternatives. Already, numerous trace gases such as H$$_2$$, CH$$_4$$, $$^{13}$$CO$$_2$$, and volatile organic compounds like acetone can be rapidly quantified in breath at concentrations below 1 ppm with SRS. With improvements in resolution and design of enhancement systems, SRS-based sensors could be scalably deployed in, e.g., pharmacies, and non-invasively screen for dozens of analytes at the parts-per-billion level. 

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3. Simulated Raman spectral analysis of organic molecules

   https://doi.org/10.1117/12.2291176  

   Ren, Jun; Tyler, Zachary; Kong, Kam; Lu, Qi; Zhao, Jian; Lu, Lu; Osiński, Marek; Arakawa, Yasuhiko; Witzigmann, Bernd (February 2018, Physics and Simulation of Optoelectronic Devices XXVI)
4. Intensity correlation analysis of Raman spectra of concentrated Ficoll solutions

   https://doi.org/10.1117/12.2609947  

   Rivera-Lopez, Yahira M.; Salih, Mohamed A.; Boukari, Fatima; Barnett, Cleon M.; Boukari, Hacene (March 2022, Proc. SPIE 11944, Multiscale Imaging and Spectroscopy III)

   Maitland, Kristen C.; Roblyer, Darren M.; Campagnola, Paul J. (Ed.)

   The intracellular environment is crowded with diverse biomacrolecules (~80-400 mg/ml), likely affecting various biological processes such as protein folding, binding of small molecules, enzymatic activity, and pathological protein aggregation. As a model we have been using solutions of Ficoll, a highly branched polysaccharide, to mimic the environment. Besides its biomedical applications (e.g. blood separation), it has been used as a macromolecular crowder in studies of protein folding and stability, cell volume signaling, tissue engineering, and nanotransport. In this study, our goal is to identify and assess Raman spectral signatures associated with Ficoll molecules and Ficoll-Ficoll interactions for future investigations of crowding effects. In addition to the Raman peaks of water (~1640 cm-1 and ~3200 cm-1) and dissolved O2 (~1556 cm-1) and N2 (~2331 cm-1) we identified a distinct Raman peak (~2900 cm-1) in the 1500-3500 cm-1 wavenumber range, which is associated with Ficoll and CH and CH2 stretching modes. As the Ficoll concentration increases, the intensity of the Ficoll Raman peaks increases while the intensity of the water Raman peaks decreases, the latter likely due to reduction of water content. Further, we have applied the intensity correlation analysis (ICA) method to assess systematic changes of Raman spectra with Ficoll concentration (up to 1000 mg/ml). ICA indicates an overall linear trend over the full wavenumber range, but also shows closed loops that can be attributed to slight changes of the profiles of certain peaks. The results demonstrate ICA as a potential insightful tool for identifying Ficoll in chemical analysis of crowded biological samples. 

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5. Thermal analysis of an α-Ga2O3 MOSFET using micro-Raman spectroscopy

   https://doi.org/10.1063/5.0164095  

   Karim, Anwarul; Song, Yiwen; Shoemaker, Daniel C; Jeon, Dae-Woo; Park, Ji-Hyeon; Mun, Jae Kyoung; Lee, Hun Ki; Choi, Sukwon (November 2023, Applied Physics Letters)

   The ultra-wide bandgap (UWBG) energy (∼5.4 eV) of α-phase Ga2O3 offers the potential to achieve higher power switching performance and efficiency than today's power electronic devices. However, a major challenge to the development of the α-Ga2O3 power electronics is overheating, which can degrade the device performance and cause reliability issues. In this study, thermal characterization of an α-Ga2O3 MOSFET was performed using micro-Raman thermometry to understand the device self-heating behavior. The α-Ga2O3 MOSFET exhibits a channel temperature rise that is more than two times higher than that of a GaN high electron mobility transistor (HEMT). This is mainly because of the low thermal conductivity of α-Ga2O3 (11.9 ± 1.0 W/mK at room temperature), which was determined via laser-based pump-probe experiments. A hypothetical device structure was constructed via simulation that transfer-bonds the α-Ga2O3 epitaxial structure over a high thermal conductivity substrate. Modeling results suggest that the device thermal resistance can be reduced to a level comparable to or even better than those of today's GaN HEMTs using this strategy combined with thinning of the α-Ga2O3 buffer layer. The outcomes of this work suggest that device-level thermal management is essential to the successful deployment of UWBG α-Ga2O3 devices. 

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