共查询到20条相似文献,搜索用时 31 毫秒
1.
R.N. Jacobs L.A. Almeida J. Markunas J. Pellegrino M. Groenert M. Jaime-Vasquez N. Mahadik C. Andrews S.B. Qadri T. Lee M. Kim 《Journal of Electronic Materials》2008,37(9):1480-1487
It is well known that the large lattice mismatch (>14%) associated with CdTe/Si, CdTe/Ge, and CdTe/GaAs composite substrates,
is a great contributor to large dislocation densities and other defects that limit the performance of HgCdTe-based infrared
detectors. Though thermal expansion mismatch is another possible contributor to material defects, little work has been done
towards documenting and understanding its effects in these systems. Here, we perform studies to determine the relative contributions
of lattice and thermal mismatch to CdTe film characteristics, including dislocation density and residual stress. Unannealed
and thermally cycled films are characterized using x-ray diffraction, defect decoration, and Nomarski and transmission electron
microscopy. For CdTe/Si, the residual stress is consistently observed to be tensile, while for CdTe/Ge and CdTe/GaAs, a compressive
residual film stress is measured. We show based on theoretically predicted stress levels that the experimental measurements
imply the dominance of thermal mismatch in the residual stress characteristics. 相似文献
2.
研究了Si衬底上外延Ge薄膜中的应变。在超高真空化学气相沉积系统中生长Ge薄膜,采用高精度X射线衍射(XRD)和拉曼散射光谱检测薄膜的组份和应变。结果表明,外延薄膜的组份为纯Ge,没有Si的扩散;Ge薄膜中存在少量应变。Ge薄膜XRD峰位和拉曼散射峰位的偏移是由残余应变引起的。定量计算了热膨胀失配引入的张应变和晶格失配引入的压应变与Ge薄膜生长参数的关系,张应变随着生长温度的升高而近似线性增加,压应变随着生长厚度的增加按反比例减小,Ge薄膜最终应变状态由两者共同决定。理论计算值与实验结果吻合良好。 相似文献
3.
GUO Zi-zheng LIANG Xi-xia BAN Shi-liang 《光电子快报》2005,1(3):164-167
In recent years ,the interest in the quantum hetero-structures composed of theⅡ-Ⅵwide gap materials haveincreased dueto potential device applications ,suchasthehigh-brightness blue/green light emitting diodes(LEDs) andlaser diodes (LDs)[1].Sincethe applicationof semiconductor materials to optoelectronic devices re-quires a precise design of the optical properties at theoperation temperature, it is i mportant to have theknowledge of the temperature effects on the opticalproperties of the mat… 相似文献
4.
W. H. Bloss F. Pfisterer M. Schubert T. Walter 《Progress in Photovoltaics: Research and Applications》1995,3(1):3-24
The R&D status of cells and modules based on hydrogenated amorphous silicon (a-Si:H) and those based on CdTe and CuInSe2 is reviewed. The stability of a-Si:H solar cells is still a major concern. Improvements have been achieved on an empirical basis by application of multijunction structures, optimization of interfaces, etc. Stabilized efficiencies of close to 10% have been reported. In parallel, the introduction of the ‘defect-pool model’ led to remarkable progress in understanding; it follows that a-SiGe:H instead of a-Si:H should be used for the i-layer (absorber). Improved cell engineering concepts, however, such as enhancement of the built-in electric field via reduction of the i-layer thickness and/or folded structures, are believed to be more promising. Polycrystalline thin-film cells based on CdTe and CuInSe2 are not affected by inherent degradation mechanisms. the specific properties of these materials demand heterojunctions, and particular problems arise due to the polycrystallinity of the films and to the lattice mismatch and mismatch of the electronic band structures of the materials involved. These are discussed in conjunction with measures currently applied for optimizing solar cell performance. Both cell types exhibit eficiencies in the range 16-17%. Estimations of production costs and energy payback times of thin-film photovoltaic modules are reviewed (even below 1 US$ Wp−1 and as low as 4 months, respectively) and environmental concerns, especially for Cd-containing cells, are summarized. 相似文献
5.
《Materials Science in Semiconductor Processing》2002,5(2-3):199-206
We report on the phase transformation behavior of Pb0.91La0.09Zr0.65Ti0.35O3 (9/65/35) PLZT films grown on r-sapphire substrates via rf-magnetron sputtering. A complex microstructure results in these films depending on deposition and annealing conditions. A random equiaxed polycrystalline grain morphology was observed after rapid thermal annealing or furnace annealing when the as-deposited films were predominantly pyrochlore. Precipitate formation (100–150 nm) was observed in PLZT films that were deposited at temperatures in excess of 490°C with a perovskite structure, after furnace annealing at 700°C. We believe that this is related to internal stresses in the films due to both the lattice mismatch and the thermal expansion mismatch between the PLZT film and the sapphire substrate. 相似文献
6.
Thin film microstructure and its properties can be effectively altered with post deposition heat treatments. In this respect, CdTe thin films were deposited on glass substrates at a substrate temperature of 200 °C using thermal evaporation technique, followed by air annealing at different temperatures from 200 to 500 °C. Structural analysis reveals that CdTe thin films have a cubic zincblend structure with two oxide phases related to CdTe2O5 and CdTeO3 at annealing temperature of 400 and 500 °C respectively. Regardless of the annealing temperature, the plane (111) was found to be the preferred orientation for all films. The crystallite size was observed to increase with annealing temperature. All films were found to display higher lattice parameters than the standard, and hence found to carry a compressive stress. Optical measurements suggest high uniformity of films both before and after post deposition heat treatment. Films annealed at 400 °C displayed superior optical properties due to its high refractive index, optical conductivity, relative density and low disorder. Furthermore, according to the compositional measurements, CdTe thin films were found to exhibit Te rich and Cd rich nature at regions near the substrate and center of the film respectively, for all annealing temperatures. However, composition of the regions near the substrate was found to become more Te rich with increasing annealing temperature. The study suggests that changing the annealing temperature as a post deposition treatment affects structural and optical properties of CdTe thin film as well as its composition. According to the observations, films annealed at 400 °C can be concluded to be the best films for photovoltaic applications due to its superior optical and structural properties. 相似文献
7.
Correlation of biaxial strains, bound exciton energies, and defect microstructures in gan films grown on AlN/6H-SiC(0001) substrates 总被引:2,自引:0,他引:2
William G. Perry T. Zheleva M. D. Bremser R. F. Davis W. Shan J. J. Song 《Journal of Electronic Materials》1997,26(3):224-231
Biaxial strains resulting from mismatches in thermal expansion coefficients and lattice parameters in 22 GaN films grown on
A1N buffer layers previously deposited on vicinal and on-axis 6H-SiC(0001) substrates were measured via changes in the c-axis
lattice parameter. A Poisson’s ratio of ν = 0.18 was calculated. The bound exciton energy (EBX) was a linear function of these strains. The shift in EBX with film stress was 23 meV/GPa. Threading dislocations densities of ~1010/cm2 and ~108/em2 were determined for GaN films grown on vicinal and on-axis SiC, respectively. A 0.9% residual compressive strain at the GaN/AIN
interface was observed by high resolution transmission electron microscopy (HRTEM). 相似文献
8.
Kwang-Chon Kim Seung Hyub Baek Hyun Jae Kim Jin Dong Song Jin-Sang Kim 《Journal of Electronic Materials》2012,41(10):2795-2798
Epitaxial CdTe thin films were grown on GaAs/Si(001) substrates by metalorganic chemical vapor deposition using thin GaAs as a buffer layer. The interfaces were investigated using high-resolution transmission electron microscopy and geometric phase analysis strain mapping. It was observed that dislocation cores exist at the CdTe/GaAs interface with periodic distribution. The spacing of the misfit dislocation was measured to be about 2?nm, corresponding to the calculated spacing of a misfit dislocation (2.6?nm) in CdTe/Si with Burgers vector of a[110]/2. From these results, it is suggested that the GaAs buffer layer effectively absorbs the strain originating from the large lattice mismatch between the CdTe thin film and Si substrate with the formation of periodic structural defects. 相似文献
9.
The development of HgCdTe detectors requires high sensitivity, small pixel size, low defect density, long-term thermal-cycling reliability, and large-area substrates. CdTe bulk substrates were initially used for epitaxial growth of HgCdTe films. However, CdTe has a lattice mismatch with long-wavelength infrared (LWIR) and middle-wavelength infrared (MWIR) HgCdTe that results in detrimental dislocation densities above mid-106 cm?2. This work explores the use of CdTe/Si as a possible substrate for HgCdTe detectors. Although there is a 19% lattice mismatch between CdTe and Si, the nanoheteroepitaxy (NHE) technique makes it possible to grow CdTe on Si substrates with fewer defects at the CdTe/Si interface. In this work, Si(100) was patterned using photolithography and dry etching to create 500-nm to 1-μm pillars. CdTe was selectively deposited on the pillar surfaces using the close-spaced sublimation (CSS) technique. Scanning electron microscopy (SEM) was used to characterize the CdTe selective growth and grain morphology, and transmission electron microscopy (TEM) was used to analyze the structure and quality of the grains. CdTe selectivity was achieved for most of the substrate and source temperatures used in this study. The ability to selectively deposit CdTe on patterned Si(100) substrates without the use of a mask or seed layer has not been observed before using the CSS technique. The results from this study confirm that CSS has the potential to be an effective and low-cost technique for selective nanoheteroepitaxial growth of CdTe films on Si(100) substrates for infrared detector applications. 相似文献
10.
<正> High qualities of GaAs layers directly grown on Si substrates have been obtained by MBE. The residual stress in those MBE grown GaAs layers on 相似文献
11.
L. Abad V. Laukhin S. Valencia A. Gaup W. Gudat L. Balcells B. Martínez 《Advanced functional materials》2007,17(18):3918-3925
Complex oxides with perovskite structure are the ideal arena to study a plethora of physical properties including superconductivity, ferromagnetism, ferroelectricity, piezoelectricity and more. Among them, transition metal oxides are especially relevant since they present large electronic correlations leading to a strong competition between lattice, charge, spin, and orbital degrees of freedom. In particular, manganese perovskites oxides exhibit half‐metallic character and colossal magnetoresistive response rendering them as the ideal materials to develop novel concepts of oxide‐electronic devices and for the study of fundamental physical interactions. Due to the close similarity between kinetic energy of charge carriers and Coulomb repulsion, tiny perturbations caused by small changes in temperature, magnetic or electric fields, strain and so forth may drastically modify the magnetic and transport properties of these materials. In particular clarifying the role of interfacial strain in manganite thin films is interesting not only for device applications but also for basic understanding of physical interactions. A better comprehension of such strongly correlated systems might lead to control the different degrees of freedom in a near future contributing to the development of the so called orbitronics, i.e. controlling and modifying at will the orbital orientation of the 3d levels in transition metals. Here we reveal the importance of interfacial strain in high quality epitaxial thin films of La2/3Ca1/3MnO3 (LCMO), grown on top of SrTiO3 (STO) and NdGaO3 (NGO) (001)‐oriented substrates. We show that in such systems interfacial strain due to lattice mismatch lifts the degeneracy of the eg and t2g orbitals close to the film/substrate interface inducing Jahn‐Teller like distortions and promoting selective orbital occupancy and the appearance of an orbital glass insulating state in an otherwise ferromagnetic metallic material. These results highlight the role of strain and identify it as a key parameter in orbital control. 相似文献
12.
Bin Cui Cheng Song Gillian A. Gehring Fan Li Guangyue Wang Chao Chen Jingjing Peng Haijun Mao Fei Zeng Feng Pan 《Advanced functional materials》2015,25(6):864-870
Electrical manipulation of lattice, charge, and spin is realized respectively by the piezoelectric effect, field‐effect transistor, and electric field control of ferromagnetism, bringing about dramatic promotions both in fundamental research and industrial production. However, it is generally accepted that the orbital of materials are impossible to be altered once they have been made. Here, electric field is used to dynamically tune the electronic‐phase transition in (La,Sr)MnO3 films with different Mn4+/(Mn3+ + Mn4+) ratios. The orbital occupancy and corresponding magnetic anisotropy of these thin films are manipulated by gate voltage in a reversible and quantitative manner. Positive gate voltage increases the proportion of occupancy of the orbital and magnetic anisotropy that were initially favored by strain (irrespective of tensile and compressive), while negative gate voltage reduces the concomitant preferential orbital occupancy and magnetic anisotropy. Besides its fundamental significance in orbital physics, these findings might advance the process towards practical oxide‐electronics based on orbital. 相似文献
13.
E. A. Irene 《Journal of Electronic Materials》1976,5(3):287-298
The mechanical stress caused by Si3N4 films on (111) oriented Si wafers was studied as a function of the Si3N4 film thickness, deposition rate, deposition temperature and film composition. The Si3N4 films were prepared by the reaction of gaseous SiH4 and NH3 in the temperature range 700–1000°C. The curvature of the Si substrates caused by the Si3N4. films is related to the film stress; the substrate curvature was measured by an optical interference technique. The measured Si3N4. film stress was found to be highly tensile with a magnitude of about 1010 dynes/cm2. For the thickness range of 2000–5000Å, there was no change in the measured stress. The total film stress was observed to decrease for decreasing deposition rate and increasing deposition temperature. A large change in film stress was observed for films containing excess Si; the stress decreased with increasing Si content. Based on published values for the thermal expansion coefficients for Si and Si3N4, a published value for Young’s Modulus for Si3N4, and the measured total stress values, a consistent argument is developed in which the total stress consists of a compressive component due to thermal expansion coefficient mismatch and a larger tensile intrinsic stress component. Both the thermal and intrinsic stress components vary with film deposition temperature in directions which decrease the total room temperature stress for higher deposition temperatures. 相似文献
14.
采用脉冲激光溅射沉积技术在LaAlO3(001)衬底上制备了一系列不同厚度(40~240 nm)的La0.67Ba0.33MnO3薄膜。通过控制薄膜的厚度,获得了不同应变态的La0.67Ba0.33MnO3薄膜。根据X射线衍射(XRD)数据详细分析了薄膜厚度变化对c轴晶格常数的影响。采用标准的直流四探针法和超导量子干涉仪分别测量了薄膜的电阻温度特性和磁化强度温度特性。研究发现,La0.67Ba0.33MnO3薄膜的居里温度和金属绝缘态转变温度随压缩应变的增大而减小,即压缩应变抑制了La0.67Ba0.33MnO3薄膜的铁磁性,降低了居里温度。这一结果与以往压缩应变增强铁磁性并提高居里温度的结论相异,不能利用Millis的应变理论模型进行定性解释。利用超巨磁电阻(CMR)薄膜材料的应变效应对eg轨道稳定性的影响对La0.67Ba0.33MnO3薄膜的异常磁电输运效应进行了解释。 相似文献
15.
M. S. Angelo B. E. McCandless R. W. Birkmire S. A. Rykov J. G. Chen 《Progress in Photovoltaics: Research and Applications》2007,15(2):93-111
The feasibility of measuring contact wetting angles to characterize processing induced changes to thin film semiconductors in CdTe/CdS solar cells is evaluated. The contact angles of water and formamide are used to determine the polar and dispersive surface energies of the thin films using two analysis methods. Changes in surface energies resulting from processing are correlated to changes in surface chemistry and structure detected by glancing incidence X‐ray diffraction (GIXRD), X‐ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Surface energies are evaluated for sputtered In2O3:SnO2, chemical surface‐deposited CdS, and physical vapor‐deposited (PVD) CdTe thin films under as‐deposited and treated conditions. Treatments include thermal anneal in air, argon, and CdCl2 ambient as well as surface etching. Indium tin oxide (ITO) and CdS films exhibit increased polar surface energy corresponding to enhanced crystallization of surfaces resulting from processing and increasing CdS growth temperature. Native oxidation of PVD CdTe (111)‐oriented film surfaces occurs rapidly and is readily detected by changes in contact angle. Surface energies of PVD (111)‐oriented CdTe stored under various humidities prior to processing are energetically similar due to native oxidation. The polar energy of CdTe surfaces is affected by the addition or removal of crystalline surface oxides during film processing. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
16.
CdTe thin films of different thicknesses were deposited on polymer substrates for flexible optical devices applications. X-ray diffractogram of different thicknesses for CdTe films are measured and their patterns exhibit polycrystalline nature with a preferential orientation along the (111) plane. The optical constants of CdTe films were calculated based on the measured transmittance spectral data using Swanepoel's method in the wavelength range 400–2500 nm. The refractive index n and absorption index k were calculated and the refractive index exhibits a normal dispersion. The refractive index dispersion data followed the Wemple–DiDomenico model based on single oscillator. The oscillator dispersion parameters and the refractive index no. at zero photon energy were determined. The possible optical transition in these films is found to be allowed direct transition with energy gap increase from 1.46 to 1.60 eV with the increase in the film thickness. CdTe/flexible substrates are good candidates in optoelectronic devices 相似文献
17.
The nanocomposite thin films of titanium dioxide (TiO2)–lead phthalocyanine (PbPc) have been prepared on glass substrates by the electron beam evaporation technique. The optical properties of TiO2/PbPc nanocomposite thin films have been investigated using a spectrophotometric measurement of the absorbance and transmittance at normal incident of light in the wavelength region 300–800 nm. Surface morphology of thin films has been characterized using field emission scanning electron microscopy (FESEM). The UV–vis analysis has been performed to determine the type of electronic transition and the optical energy band gap. The analysis of the spectral behavior of the absorption coefficient in the intrinsic absorption region reveals that the absorption mechanism is due to direct transition. Moreover, by studying the absorption coefficient spectra just below the fundamental absorption edge, the width of band tails of localized states (Urbach energy), steepness parameter and width of the defect states have been evaluated. The obtained results of this novel nanocomposite (TiO2/PbPc) support the desirable features for the optoelectronic devices. 相似文献
18.
W. Lei R. J. Gu J. Antoszewski J. Dell L. Faraone 《Journal of Electronic Materials》2014,43(8):2788-2794
In this work, GaSb is proposed as a new alternative substrate for the growth of HgCdTe via molecular beam epitaxy (MBE). Due to the smaller mismatch in both lattice constant and coefficient of thermal expansion between GaSb and HgCdTe, GaSb presents a better alternative substrate for the epitaxial growth of HgCdTe, in comparison to alternative substrates such as Si, Ge, and GaAs. In our recent efforts, a CdTe buffer layer technology has been developed on GaSb substrates via MBE. By optimizing the growth conditions (mainly growth temperature and VI/II flux ratio), CdTe buffer layers have been grown on GaSb substrates with material quality comparable to, and slightly better than, CdTe buffer layers grown on GaAs substrates, which is one of the state-of-the-art alternative substrates used in growing HgCdTe for the fabrication of mid-wave infrared detectors. The results presented in this paper indicate the great potential of GaSb to become the next generation alternative substrate for HgCdTe infrared detectors, demonstrating MBE-grown CdTe buffer layers with rocking curve (double crystal x-ray diffraction) full width at half maximum of ~60 arcsec and etch pit density of ~106 cm?2. 相似文献
19.
David Boldrin Freya Johnson Ryan Thompson Andrei P. Mihai Bin Zou Jan Zemen Jack Griffiths Patrik Gubeljak Kristian L. Ormandy Pascal Manuel Dmitry D. Khalyavin Bachir Ouladdiaf Navid Qureshi Peter Petrov Will Branford Lesley F. Cohen 《Advanced functional materials》2019,29(40)
Multicomponent magnetic phase diagrams are a key property of functional materials for a variety of uses, such as manipulation of magnetization for energy efficient memory, data storage, and cooling applications. Strong spin‐lattice coupling extends this functionality further by allowing electric‐field‐control of magnetization via strain coupling with a piezoelectric. Here this work explores the magnetic phase diagram of piezomagnetic Mn3NiN thin films, with a frustrated noncollinear antiferromagnetic (AFM) structure, as a function of the growth induced biaxial strain. Under compressive strain, the films support a canted AFM state with large coercivity of the transverse anomalous Hall resistivity, ρxy, at low temperature, that transforms at a well‐defined Néel transition temperature (TN) into a soft ferrimagnetic‐like (FIM) state at high temperatures. In stark contrast, under tensile strain, the low temperature canted AFM phase transitions to a state where ρxy is an order of magnitude smaller and therefore consistent with a low magnetization phase. Neutron scattering confirms that the high temperature FIM‐like phase of compressively strained films is magnetically ordered and the transition at TN is first‐order. The results open the field toward future exploration of electric‐field‐driven piezospintronic and thin film caloric cooling applications in both Mn3NiN itself and the broader Mn3AN family. 相似文献
20.
S. Neretina Q. Zhang R. A. Hughes J. F. Britten N. V. Sochinskii J. S. Preston P. Mascher 《Journal of Electronic Materials》2006,35(6):1224-1230
Cadmium telluride (CdTe) is the most well-established II–VI compound largely due to its use as a photonic material. Existing
applications, as well as those under consideration, are demanding increasingly stringent control of the material properties.
The deposition of high-quality thin films is of utmost importance to such applications. In this regard, we present a report
detailing the role of lattice mismatch in determining the film quality. Thin films were deposited on a wide variety of substrate
materials using the pulsed laser deposition (PLD) technique. Common to all substrates was the strong tendency toward the preferential
alignment of CdTe’s (111) planes parallel to the substrate’s surface. X-ray diffraction analysis, however, revealed that the
crystalline quality varied dramatically depending upon the substrate used with the best results yielding a single-crystal
film. This tendency also manifested itself in the surface morphology with higher structural perfection yielding smoother surfaces.
The film quality showed a strong correlation with lattice mismatch. Texture analysis using the [111] pole figure confirmed
that improvements in the lattice mismatch led to a higher degree of in-plane alignment of the (111) grains. 相似文献