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Effect of low-energy ion impact on the structure of hexagonal boron nitride films studied in surface-wave plasma
摘要： A high‐density surface‐wave plasma source is used to deposit hexagonal boron nitride (hBN) films in a gas mixture of He, H2, N2, Ar, and BF3 under a high ion flux condition using low‐energy ion irradiation. The ion energy is controlled between around zero and 100 eV by applying a negative or positive bias voltage to a substrate, while the ion flux is increased by locating a substrate upstream in the diffusive plasma. For ion energies above ～37 eV, the structure of the films depends upon ion energy more than substrate temperature, typical of subplantation processes. As a result, the structural order and crystallinity of sp2‐bonded phase in the films characterized by Fourier transform infrared spectroscopy and X‐ray diffraction are increased with decreasing ion energy, while the mass density of the films characterized by X‐ray reflectivity is retained relatively high with a slight dependence upon ion energy.
关键词： surface‐wave plasma,Fourier transform infrared spectroscopy (FTIR),chemical vapor deposition (CVD),hexagonal boron nitride (hBN),X‐ray diffraction (XRD),X‐ray reflectivity (XRR)
更新于2025-09-23 15:21:21
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Fourier Transform Infrared Spectroscopy: Applications in Medicine
摘要： Fourier transform infrared spectroscopy (FTIR) is rapidly gaining ground in modern clinical research. This technique is useful for understanding a wide variety of applications ranging from characterization and quality control of various compounds to biomedicine. Importantly, biological materials like proteins, carbohydrates, lipids and nucleic acids have unique structures so it is possible to obtain spectral fingerprints corresponding to their functional groups. FTIR spectroscopic techniques generate an immediate appeal in the field of biology and medicine because of their fast and non-invasive nature. It allows easy visualization of cellular components based on their intrinsic properties and chemical composition. It provides a potential route to screen diagnostic markers for diseases like cancer. FTIR spectroscopy is also considered as a useful tool for analysis of the chemical composition of human calculi. Analysis of stone samples from recurrent stone formers by FTIR may provide a clue to effective prevention of stone recurrence [1]. Fourier transform infrared (FT-IR) spectroscopy has proven to be a fundamental and valuable technique in biology and medicine due to its high sensitivity to detecting changes in the functional groups belonging to tissue components such as lipids, proteins and nucleic acids [2]. Infrared spectra of human and animal tissues could provide information on the molecular structure of tissues. FT-IR has been extensively applied for the determination of a biochemical metabolite in biological fluids. Diagnosis of various types of malignancies such as lung, breast, skin, cervical and colon cancers is already reported in the literature. The spectra are analysed for changes in levels of molecules such as RNA, DNA, phosphates, and carbohydrates. Variation of the RNA/DNA ratio as measured at 1121/1020 cm-1 generally show higher ratio for malignant tissues compared to their non-malignant counterpart. Changes in the spectra of malignant samples were also observed in the symmetric and asymmetric stretching bands of the phosphodiester backbones of nucleic acids, the CH stretching region, the C-O stretching bands of the C-OH groups of carbohydrates and cellular protein residuals, and the pressure dependence of the CH2 stretching mode [3]. The changes in the FTIR spectra correlate to modification of bases and sugars, and redistribution of the H-bond network. The loss/change in the covalent bonds due to damage in the primary, secondary and tertiary structure of nucleic acids can be observed in the spectra. These changes involved the phosphate and C-O stretching bands, the CH stretch region, and the pressure dependence of the CH2 bending and C=O stretching modes. FTIR micro spectroscopy has also been used as a fast diagnostic technique to identify drugs targeting specific molecular pathways causing chronic myeloid leukaemia. Chemometric data analysis was used to assess drug compounds in ex vivo cancer cells [4]. Substantial progress has been made in incorporating advances in computational methods into the system to increase the sensitivity of the entire setup, making it an objective and sensitive technique suitable for automation to suit the demands of the medical community. FTIR spectroscopy provides the possibility of obtaining information on molecular composition and structure at the level of single cell within a time-scale of few seconds-minutes and to perform qualitative and quantitative multi-component analyses. It helps in automated pattern recognition and objective classifications of samples with minimal and label-free sample treatment. The technical improvements will progressively increase the number of potential applications of micro FT-IR to cancer research and clinical diagnosis. It may be hoped that the future pre-clinical and clinical trials will include sample evaluation utilizing this technique in order to obtain data necessary to validate the use of micro FT-IR spectroscopy in a clinical context. In fact, this appears to be the most important way to reduce the high level of skepticism of many biologists and pathologists about an old technology that has been designed and improved mainly for applications in clinical diagnosis including cancer research.
关键词： cancer research,biomedicine,clinical diagnosis,Fourier transform infrared spectroscopy,FTIR,clinical research
更新于2025-09-09 09:28:46