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1.
V. A. Volodin E. B. Gorokhov M. D. Efremov D. V. Marin D. A. Orekhov 《JETP Letters》2003,77(8):411-414
Germanium nanocrystals were formed in a GeO2 film during the process of germanium monoxide gas-phase deposition onto a sapphire substrate and studied by photoluminescence (PL) and Raman scattering spectroscopy. A PL peak in this heterosystem was observed in the visible region at room temperature. The sizes of Ge nanocrystals were estimated from the position of a Raman peak corresponding to scattering by localized optical phonons in germanium. The PL peak position calculated with allowance for the electron and hole size quantization in Ge nanocrystals coincides well with the experimentally observed position of this peak. 相似文献
2.
Using the methods of scanning and spectral laser ellipsometry and Raman scattering spectroscopy, GeO2 films containing Ge nanoclusters with a Ge/GeO2 mole ratio of 1: 1 are studied. A substantial difference is found between the experimental spectral dependence of the complex permittivity of the films and the one calculated for the effective medium in the Bruggeman model. The distinction can be qualitatively explained by the influence of the quantum-size effect. With the use of theoretical models for quantitative analysis, this approach will make it possible to determine the phase composition and dimensions of the nanoclusters of germanium in a contactless way without destructing the film. 相似文献
3.
Nobutoshi Arai Hiroshi Tsuji Masayuki Ohsaki Toyotsugu Ishibashi Junzo Ishikawa 《Applied Surface Science》2009,256(4):954-957
We have investigated cathodeluminescence (CL) of Ge implanted SiO2:Ge and GeO2:Ge films. The GeO2 films were grown by oxidation of Ge substrate at 550 °C for 3 h in O2 gas flow. The GeO2 films on Ge substrate and SiO2 films on Si substrate were implanted with Ge-negative ions. The implanted Ge atom concentrations in the films were ranging from 0.1 to 6.0 at%. To produce Ge nanoparticles the SiO2:Ge films were thermally annealed at various temperatures of 600-900 °C for 1 h in N2 gas flow. An XPS analysis has shown that the implanted Ge atoms were partly oxidized. CL was observed at wavelengths around 400 nm from the GeO2 films before and after Ge−-implantation as well as from SiO2:Ge films. After Ge−-implantation of about 0.5 at% the CL intensity has increased by about four times. However, the CL intensity from the GeO2:Ge films was several orders of magnitude smaller than the intensity from the 800 °C-annealed SiO2:Ge films with 0.5 at% of Ge atomic concentration. These results suggested that the luminescence was generated due to oxidation of Ge nanoparticles in the SiO2:Ge films. 相似文献
4.
Transitions of microstructure and photoluminescence properties of the Ge/ZnO multilayer films in certain annealing temperature region 总被引:1,自引:0,他引:1
Tianhang Zheng Ziquan Li Jiankang Chen Kai Shen Kefei Sun 《Applied Surface Science》2006,252(24):8482-8486
The Ge/ZnO multilayer films have been prepared by rf magnetron sputtering. The effects of annealing on the microstructure and photoluminescence properties of the multilayers have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectrometry and photoluminescence (PL) spectrometry. The investigation of structural properties indicates that Zn2GeO4 has been formed with (2 2 0) texture and Zn deficiency from Ge/ZnO multilayer films in the process of annealing. However, lower Zn/Ge ratio can be improved by annealing. The annealed multilayers show three main emission bands at 532, 700, and 761 nm, which originate from the transition between oxygen vacancy () and Zn vacancies (VZn), the radiative recombination of quantum-confined excitons (QCE) in Ge nanocrystals, and the optical transition in the GeO color centers, respectively. Finally, the fabrication of thin film Zn2GeO4 from Ge/ZnO multilayer films by annealing at low temperature provides another approach to prepare the green-emitting oxide phosphor film:Zn2GeO4:Mn. 相似文献
5.
We have investigated the origin of room temperature photoluminescence from ion-beam synthesized Ge nanocrystals (NCs) embedded in SiO2 using steady state and time-resolved photoluminescence (PL) measurements. Ge NCs of diameter 4-13 nm were grown embedded in a thermally grown SiO2 layer by Ge+ ion implantation and subsequent annealing. Steady state PL spectra show a peak at ∼2.1 eV originating from Ge NCs and another peak at ∼2.3 eV arising from ion-beam induced defects in the SiO2 matrix. Time-resolved PL studies reveal double exponential decay dynamics on the nanoseconds time scale. The faster component of the decay with a time constant τ1∼3.1 ns is attributed to the nonradiative lifetime, since the time constant reduces with increasing defect density. The slower component with time constant τ2∼10 ns is attributed to radiative recombination at the Ge NCs. Our results are in close agreement with the theoretically predicted radiative lifetime for small Ge NCs. 相似文献
6.
The photoluminescence (PL) at ∼2.2-2.3 eV from Ge-based nanocrystalline materials is described in the literature as nanocrystal size-independent. We have observed visible luminescence from two different types of stain-etched Ge samples, one prepared after Sendova-Vassileva et al. (Thin Solid Films 255 (1995) 282) in a solution of H2O2:HF at 50:1 volume ratio, and the other in a solution of HF:H3PO4:H2O2 at 34:17:1 volume ratio. Energy dispersive X-ray analysis (EDX), Raman and FTIR spectroscopy, and the near edge X-ray absorption structure (XANES), indicate that the chemically etched Ge layers of the former type of samples are composed of non-stoichometric Ge oxides, i.e. GeOx (0<x<2), and free from any Ge nanoconstructions. It is also suggested from XANES that the latter type of chemically etched Ge samples comprise 8-9 nm nanocrystals of Ge, surface-covered with mainly oxygen. Photoluminescence occurred at ∼2.3 eV for all samples. The PL behavior of the latter type of chemically etched Ge on annealing in different chemical environments (air or H) allowed us to conclude that the PL from these materials, as well as that from those Ge-based nanocrystalline materials reported in the literature, is from GeOxs. 相似文献
7.
K. N. Astankova D. V. Sheglov E. B. Gorokhov V. A. Volodin A. G. Cherkov A. V. Latyshev M. Vergnat 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(5):773-780
The possibility of forming the Ge-based wires with the nanoscale’s lateral resolution using the local modification of GeO(sol) films by a scanning probe microscope was demonstrated for the first time. The property of the solid germanium monoxide films,
namely, their metastability, was used to decompose the GeO film on Ge and GeO2 by running the high-density electric current under the probe of the atomic force microscope. 相似文献
8.
Chie Hosokawa Suguru N. Kudoh Mariko Suzuki Ai Kiyohara Yoichiroh Hosokawa Kazunori Okano Hiroshi Masuhara Takahisa Taguchi 《Applied Physics A: Materials Science & Processing》2010,101(2):423-428
The surface of a single-crystal germanium wafer was transformed to crystals of germanium fluorides and oxides upon exposure
to a vapor of HF and HNO3 chemical mixture. Structure analysis indicates that the transformation results in a germanate polycrystalline layer consisting
of germanium oxide and ammonium fluogermanate with preferential crystal growth orientation in 〈101〉 direction. Local vibrational
mode analysis confirms the presence of N–H and Ge–F vibrational modes in addition to Ge–O stretching modes. Energy dispersive
studies reveal the presence of hexagonal α-phase GeO2 crystal clusters and ammonium fluogermanates around these clusters in addition to a surface oxide layer. Electronic band
structure as probed by ellipsometry has been associated with the germanium oxide crystals and disorder-induced band tailing
effects at the interface of the germanate layer and the bulk Ge wafer. The acid vapor exposure causes Ge surface to emit yellow
photoluminescence at room temperature. 相似文献
9.
In the current work, zinc oxide (ZnO) nano/microstructures are synthesized using a modified thermal-evaporation process by introducing germanium oxide (GeO2) powder mixed with metallic Zn powder as the raw material. Without the use of any catalyst and oxygen flow in the furnace system, GeO2 is utilized to provide an oxygen source for the growth of ZnO structure. The samples are treated by different temperatures ranging from 500 to 900 °C. Morphology, phase structure, and photoluminescence properties are investigated by scanning electron microscopy (SEM), X-ray diffractometer (XRD) and photoluminescence (PL) spectrometer. The structures and morphologies of the samples were found to vary with growth temperature. The XRD diffraction peaks show that the films grown at temperature from 600 to 800 °C consist of hexagonal wurtzite ZnO structures. Room-temperature PL measurement revealed ZnO spectra representing two bands: near-band-edge emission in the ultraviolet (UV) region and broad deep-level emission centered at about 500 nm. The strong UV emission in the PL spectra indicates that the GeO2 supplies sufficient oxygen for formation of ZnO structures with few oxygen vacancies. The growth mechanism and the roles of GeO2 for formation of ZnO structures are discussed in detail. 相似文献
10.
I. Cabria M. J. López J. A. Alonso N. H. March 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(4):105
In silica (SiO2) and in most silicates, atomic associations exist with composition SiO4 and a structure with four O atoms in tetrahedral coordination around the Si atom. A similar feature is observed in germania
(GeO2) and some solids containing Ge instead of Si, although the number of phases containing GeO4 tetrahedra is smaller. In contrast, and in spite of the fact that C is in the same column of the periodic table as Si and
Ge, CO2 is a molecular solid, and crystalline and amorphous phases of CO2 showing CO4 tetrahedra are only obtained under extremely high pressures. We have investigated the relation between free SiO4, GeO4 and CO4 clusters and the tetrahedral associations found in the solids mentioned above. The lowest energy structure of those three
free clusters is planar, but they have near-tetrahedral and distorted-tetrahedral isomers. The promotion energy from the planar
structure to the distorted tetrahedral is low in SiO4, large in CO4, and intermediate in GeO4. This correlates with the facility to form tetrahedral associations in the solids. 相似文献
11.
We have studied photoluminescence and thermoluminescence (PL and TL) in CaGa2Se4:Eu crystals in the temperature range 77–400 K. We have established that broadband photoluminescence with maximum at 571 nm
is due to intracenter transitions 4f6 5d–4f7 (8S7/2) of the Eu2+ ions. From the temperature dependence of the intensity (log I–103/T), we determined the activation energy (E
a = 0.04 eV) for thermal quenching of photoluminescence. From the thermoluminescence spectra, we determined the trap depths:
0.31, 0.44, 0.53, 0.59 eV. The lifetime of the excited state 4f6 5d of the Eu2+ ions in the CaGa2Se4 crystal found from the luminescence decay kinetics is 3.8 μsec.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 112–116, January–February, 2009. 相似文献
12.
High‐quality Inx Al1–xN (0.71 ≤ xIn ≤ 1.00) nanocolumns (NCs) have been grown on Si(111) substrates by rf‐plasma‐assisted molecular‐beam epitaxy (rf‐MBE). Low‐temperature photoluminescence (LT‐PL) spectra of various In‐rich InAlN NCs were measured at 4 K and single peak PL emissions were observed in the wavelength region from 0.89 µm to 1.79 µm. Temperature‐dependent PL spectra of In0.92Al0.08N NCs were studied and the so‐called “S‐shape” (decrease–increase–decrease) PL peak energy shift was observed with increasing temperature. This shift indicates the carrier localization induced by the In segregation effect and is different from the anomalous blue shift frequently observed in InN films and nanowires with high residual carrier concentra‐ tions. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
Amita Verma N. Karar A. K. Bakhshi Harish Chander S. M. Shivaprasad S. A. Agnihotry 《Journal of nanoparticle research》2007,9(2):317-322
Homogenous nano structured CeO2 films have been prepared by a sol-gel process using different mole ratios of citric acid as additive. XPS studies clearly
illustrate an increase in Ce3+ proportion upon the use of higher citric acid content for the deposition of films. The crystallite sizes in the films lie
in the nanorange. Photoluminescence emission in the films is attributed to various defects resulting from crystallization.
Lowest transparency, high Ce3+ content and optimum sized crystallites in CeO2 (1:1.5) films have led to its highest PL characteristics. Ce3+ chemical state is the major contributor to the PL activity of these films. The SEM micrographs show a reduced level of CeO2 agglomeration in the films deposited using higher citric acid contents. A comparison of different properties of CeO2 films deposited using citric acid and CeO2–TiO2 films has also been made.
相似文献
14.
I. N. Ogorodnikov V. A. Pustovarov S. A. Yakovlev L. I. Isaenko S. A. Zhurkov 《Physics of the Solid State》2012,54(4):735-740
This paper reports on a study of the dynamics of electronic excitations in KBe2BO3F2 (KBBF) crystals by low-temperature luminescent vacuum ultraviolet spectroscopy with nanosecond time resolution under photoexcitation
by synchrotron radiation. The first data have been obtained on the kinetics of photoluminescence (PL) decay, time-resolved
PL spectra, time-resolved PL excitation spectra, and reflection spectra at 7 K; the estimation has been performed for the
band gap E
g = 10.6−11.0 eV; the predominantly excitonic mechanism for PL excitation at 3.88 eV has been identified; and defect luminescence
bands at 3.03 and 4.30 eV have been revealed. The channels of generation and decay of electronic excitations in KBBF crystals
have been discussed. 相似文献
15.
Nanocrystals of Ge surrounded by a germanium oxide matrix have been formed by dry thermal oxidation of polycrystalline SiGe layers. Violet (3.16 eV) luminescence emission is observed when Ge nanocrystals, formed by the oxidation of the Ge segregated during the oxidation of the SiGe layer, are present, and vanishes when all the Ge has been oxidized forming GeO2. Based on the evolution of the luminescence intensity and the structure of the oxidized layer with the oxidation time, the recombination of excitons inside the nanocrystals and the presence of defects in the bulk oxide matrix are ruled out as sources of the luminescence. The luminescence is attributed to recombination in defects at the Ge sub-oxide interface between the Ge nanocrystals and the surrounding oxide matrix, which is GeO2. 相似文献
16.
S. Das R. K. Singha S. Manna S. Gangopadhyay A. Dhar S. K. Ray 《Journal of nanoparticle research》2011,13(2):587-595
We have grown Ge nanocrystals (NCs) (4.0–9.0 nm in diameter) embedded in high-k HfO2 matrix for applications in floating gate memory devices. X-ray photoelectron spectroscopy has been used to probe the local
chemical bonding of Ge NCs. The analysis of Ge–Ge phonon vibration using Raman spectroscopy has shown the formation of compressively
stressed Ge NCs in HfO2 matrix. Frequency dependent electrical properties of HfO2/Ge-NCs in HfO2/HfO2 sandwich structures have been studied. An anticlockwise hysteresis in the capacitance–voltage characteristics suggests electron
injection and trapping in embedded Ge NCs. The role of interface states and deep traps in the devices has been thoroughly
examined and has been shown to be negligible on the overall device performance. 相似文献
17.
Photoacoustic spectroscopy (PAS) is one of the important branches of spectroscopy, which enables one to detect light-induced
heat production following the absorption of pulsed radiation by the sample. As2S3, As2Se3 and GeSe2 exhibit a wide variety of photo-induced phenomena that enable them to be used as optical imaging or storage medium and various
electronic devices, including electro-optic information storage devices and optical mass memories. Therefore, accurate measurement
of thermal properties of semiconducting films is necessary to study the memory density. The thermal conductivity of thin films
of As2S3 (thickness 100 μm and 80 μm), As2Se3 (thickness 100 μm and 80 μm) and GeSe2 (thickness 120 μm and 100 μm) has been measured using PAS technique. Our result shows that the thermal conductivity of thicker films is larger than the
thinner films. This can be explained by the thermal resistance effect between the film and the surface of the substrate.
相似文献
18.
G. Anoop K. Mini Krishna M.K. Jayaraj 《Applied Physics A: Materials Science & Processing》2008,90(4):711-715
Thin films of ZnGa2O4:Mn2+ were deposited on quartz substrates using an rf magnetron sputtering technique. The sputtering target, ZnGa2O4 doped with 2 at. % manganese, was synthesized by a high temperature solid state reaction. Two different dopant sources were
used to incorporate the dopant ions into the target, namely, manganese acetate and manganese oxide. The structural and optical
properties of the thin films were studied using XRD, PL and transmission spectra. Polycrystalline ZnGa2O4:Mn with a spinel structure could be grown at an optimized substrate–target distance even at room temperature. No luminescence
was observed in the as-deposited films grown using (CH3COO)2Mn as the dopant source in the target. Substrate heating or post-deposition annealing in the reducing ambient didn’t impart
any luminescence to the films, ruling out the possibility of Mn2+ incorporation in the films. However, when using MnO as the manganese source in the target, the as-deposited films exhibited
green photoluminescent emission (peak maximum at 508 nm) for substrate temperatures at and above 500 °C. This suggests that,
in thin films, Mn incorporation and subsequent luminescent outcome is strongly influenced by the dopant source, which is quite
different from the bulk phosphor behavior.
PACS 81.15.Cd; 78.55.-m; 85.60.-q 相似文献
19.
A. K. Panchal D. K. Rai Meril Mathew C. S. Solanki 《Journal of nanoparticle research》2011,13(6):2469-2473
40 alternate a-Si/SiN
x
multilayer are incorporated as an absorber layer in a p–i–n solar cell. The device is fabricated using hot-wire chemical
vapor deposition (HWCVD) technique. The structure of the multilayer film is examined by high resolution transmission electron
microscopy (HR-TEM) which shows distinct formation of alternate a-Si and SiN
x
layers. The a-Si and SiN
x
layers have thickness of ~3.5 and 4 nm, respectively. The photoluminescence (PL) of multilayer film shows bandgap energy
of ~2.52 eV, is larger than that of the c-Si and a-Si. Dark and illuminated current–voltage (I–V) characterization of the ML films shows that these ML are photosensitive. In the present work, it is seen that the p–i–n
structure with i-layer as ML quantum well (QW) structures show photovoltaic effect with relatively high open-circuit voltage
(V
OC). The increment of bandgap energy in PL and high V
OC of the device is attributed to the quantum confinement effect (QCE). 相似文献
20.
The oriented ZnO nanorod arrays have been synthesized on a silicon wafer that coated with TiO2 films by aqueous chemical method. The morphologies, phase structure and the photoluminescence (PL) properties of the as-obtained
product were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffractometer (XRD), transmission
electron microscope (TEM) and PL spectrum. The nanorods were about 100 nm in diameter and more than 1 μm in length, which
possessed wurtzite structure with a c axis growth direction. The room-temperature PL measurement of the nanorod arrays showed strong ultraviolet emission. The
effect of the crystal structure and the thickness of TiO2 films on the morphologies of ZnO nanostructures were investigated. It was found that the rutile TiO2 films were appropriate to the oriented growth of ZnO nanorod arrays in comparison with anatase TiO2 films. Moreover, flakelike ZnO nanostructures were obtained with increasing the thickness of anatase TiO2 films. 相似文献