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Hard X‐ray photoelectron spectroscopy study of core level shifts at buried GaP/Si(001) interfaces. SURF INTERFACE ANAL 2020. [DOI: 10.1002/sia.6829] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Precise determination of surface band bending in Ga-polar n-GaN films by angular dependent X-Ray photoemission spectroscopy. Sci Rep 2019; 9:16969. [PMID: 31740691 PMCID: PMC6861320 DOI: 10.1038/s41598-019-53236-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 10/29/2019] [Indexed: 11/24/2022] Open
Abstract
We present a systematic study of surface band bending in Ga-polar n-GaN with different Si doping concentrations by angular dependent X-ray photoelectron spectroscopy (ADXPS). The binding energies of Ga 3d and N 1 s core levels in n-GaN films increase with increasing the emission angle, i. e., the probing depth, suggesting an upward surface band bending. By fitting the Ga 3d core level spectra at different emission angles and considering the integrated effect of electrostatic potential, the core level energy at the topmost surface layer is well corrected, therefore, the surface band bending is precisely evaluated. For moderately doped GaN, the electrostatic potential can be reflected by the simply linear potential approximation. However, for highly doped GaN samples, in which the photoelectron depth is comparable to the width of the space charge region, quadratic depletion approximation was used for the electrostatic potential to better understand the surface band bending effect. Our work improves the knowledge of surface band bending determination by ADXPS and also paves the way for studying the band bending effect in the interface of GaN based heterostructures.
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Upadhyaya K, S S, Ayachit N, Shivaprasad SM. Charge transfer-induced enhancement of a Raman signal in a hybrid Ag–GaN nanostructure. RSC Adv 2019; 9:28554-28560. [PMID: 35529610 PMCID: PMC9071005 DOI: 10.1039/c9ra04097h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 08/12/2019] [Indexed: 11/21/2022] Open
Abstract
A hybrid system consisting of Ag nanoparticles dispersed onto a GaN nanowall network (GaN NWN) exhibited characteristic optical properties and electronic band structure. Surface-sensitive XPS studies of this high-surface-area system revealed the presence of a high surface charge carrier concentration due to dangling bonds, which resulted in a high metal-like surface conductivity. The low coverage of absorbed Ag led to the nanocluster formation, facilitating charge transfer from GaN to Ag, and thereby further increasing the surface charge carriers. Photoluminescence studies revealed the presence of a high density of band tail states at the conduction band, which is significantly (14-fold) larger than in the GaN epilayer. Raman studies show an increase (2.46-fold) in the interfacial strain at the Ag/GaN interface after the deposition of the Ag nanoparticles. We show that these surface modifications increase the density of hot spots, resulting in an intense Raman signal with an enhancement factor of 107. The role of the charge transfer between Ag nanoparticles and GaN NWN in the enhancement of Raman signal has been demonstrated. The optical properties and electronic band structure of Ag nanoparticles dispersed on a GaN nanowall network were studied. High metal like surface conductivity was revealed, and charge transfer between Ag and GaN was involved in the enhancement of Raman signals.![]()
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Affiliation(s)
- Kishor Upadhyaya
- Thin Films Lab
- Centre for Materials Science
- Department of Physics
- B. V. Bhoomaraddi College of Engineering and Technology (Presently known as K. L. E. Technological University)
- Hubballi – 580031
| | - Sharvani S
- Chemistry and Physics of Materials Unit
- Jawaharlal Nehru Centre for Advanced Scientific Research
- Bangalore-560064
- India
| | - Narasimha Ayachit
- Centre for Materials Science
- K. L. E. Technological University
- B. V. B. Campus
- Hubballi – 580031
- India
| | - S. M. Shivaprasad
- Chemistry and Physics of Materials Unit
- Jawaharlal Nehru Centre for Advanced Scientific Research
- Bangalore-560064
- India
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Cricenti A, Generosi R, Luce M, Perfetti P, Margaritondo G, Talley D, Sanghera JS, Aggarwal ID, Tolk NH, Congiu-Castellano A, Rizzo MA, Piston DW. Chemically resolved imaging of biological cells and thin films by infrared scanning near-field optical microscopy. Biophys J 2003; 85:2705-10. [PMID: 14507733 PMCID: PMC1303494 DOI: 10.1016/s0006-3495(03)74693-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The infrared (IR) absorption of a biological system can potentially report on fundamentally important microchemical properties. For example, molecular IR profiles are known to change during increases in metabolic flux, protein phosphorylation, or proteolytic cleavage. However, practical implementation of intracellular IR imaging has been problematic because the diffraction limit of conventional infrared microscopy results in low spatial resolution. We have overcome this limitation by using an IR spectroscopic version of scanning near-field optical microscopy (SNOM), in conjunction with a tunable free-electron laser source. The results presented here clearly reveal different chemical constituents in thin films and biological cells. The space distribution of specific chemical species was obtained by taking SNOM images at IR wavelengths (lambda) corresponding to stretch absorption bands of common biochemical bonds, such as the amide bond. In our SNOM implementation, this chemical sensitivity is combined with a lateral resolution of 0.1 micro m ( approximately lambda/70), well below the diffraction limit of standard infrared microscopy. The potential applications of this approach touch virtually every aspect of the life sciences and medical research, as well as problems in materials science, chemistry, physics, and environmental research.
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Affiliation(s)
| | | | - Marco Luce
- Istituto di Stuttura della Materia, Rome, Italy
| | | | - Giorgio Margaritondo
- Institut de Physique Appliquée, Ecole Polytecnique Fédérale, Lausanne, Switzerland
| | - David Talley
- Optical Sciences Division, U.S. Naval Research Laboratory, Washington, District of Columbia
| | - Jas S. Sanghera
- Optical Sciences Division, U.S. Naval Research Laboratory, Washington, District of Columbia
| | - Ishwar D. Aggarwal
- Optical Sciences Division, U.S. Naval Research Laboratory, Washington, District of Columbia
| | - Norman H. Tolk
- Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee
| | | | - Megan A. Rizzo
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - David W. Piston
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
- Address reprint requests to David W. Piston, 702 Light Hall, Vanderbilt University, Nashville, TN 37232-0615. Tel.: 615-322-7030; Fax: 615-322-7236.
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Cricenti A, Generosi R, Luce M, Perfetti P, Margaritondo G, Talley D, Sanghera JS, Aggarwal ID, Gilligan JM, Tolk NH. Spectroscopic scanning near-field optical microscopy with a free electron laser: CH2 bond imaging in diamond films. J Microsc 2001; 202:446-50. [PMID: 11309110 DOI: 10.1046/j.1365-2818.2001.00874.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hydrogen chemistry in thin films and biological systems is one of the most difficult experimental problems in today's science and technology. We successfully tested a novel solution, based on the spectroscopic version of scanning near-field optical microscopy (SNOM). The tunable infrared radiation of the Vanderbilt free electron laser enabled us to reveal clearly hydrogen-decorated grain boundaries on nominally hydrogen-free diamond films. The images were obtained by SNOM detection of reflected 3.5 microm photons, corresponding to the C-H stretch absorption, and reached a lateral resolution of 0.2 microm, well below the lambda/2 (lambda = wavelength) limit of classical microscopy.
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Affiliation(s)
- A Cricenti
- Istituto di Stuttura della Materia, via Fosso del Cavaliere 100, 00133 Roma, Italy
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Cricenti A, Generosi R, Barchesi C, Luce M, Rinaldi M, Coluzza C, Perfetti P, Margaritondo G, Schaafsma D, Aggarwal I, Gilligan J, Tolk N. First Experimental Results with the Free Electron Laser Coupled to a Scanning Near-Field Optical Microscope. ACTA ACUST UNITED AC 1998. [DOI: 10.1002/(sici)1521-396x(199812)170:2<241::aid-pssa241>3.0.co;2-a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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