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1.
The best films for thermoelectric applications near room temperature are based on the compounds Bi2Te3, Sb2Te3, and Bi2Se3, which as single crystals have distinct anisotropy in their electrical conductivity σ regarding the trigonal c-axis, whereas the Seebeck coefficient S is nearly isotropic. For p- and n-type alloys, P
⊥c > P
||c, and the power factors P
⊥c of single crystals are always higher compared with polycrystalline films, where the power factor is defined as P = S
2
σ, ⊥c and ||c are the direction perpendicular and parallel to the c-axis, respectively. For the first time in sputter-deposited
p-type (Bi0.15Sb0.85)2Te3 and n-type Bi2(Te0.9Se0.1)3 thin films, the anisotropy of the electrical conductivity has been measured directly as it depends on the angle φ between the electrical current and the preferential orientation of the polycrystals (texture) using a standard four-probe
method. The graphs of σ(φ) show the expected behavior, which can be described by a weighted mixture of σ
⊥c and σ
||c contributions. Because (σ
⊥c/σ
||c)
p
< (σ
⊥c/σ
||c)
n
, the n-type films have stronger anisotropy than the p-type films. For this reason, the angular weighted contributions of P
||c lead to a larger drop in the power factor of polycrystalline n-type films compared with p-type films. 相似文献
2.
V. Svilan K.P. Rodbell L.A. Clevenger C. Cabral R.A. Roy C. Lavoie J. Jordan-Sweet J. M. E. Harper 《Journal of Electronic Materials》1997,26(9):1090-1095
Detailed analysis of the crystallographic texture of C54 TiSi2 was performed and showed a strong correlation between the geometry of the silicide structures and preferential crystallographic
orientation. The study was undertaken on blanket and patterned TiSi2 films formed in the reaction between 32 nm of Ti and undoped polycrystalline silicon using both in situ x-ray diffraction during heating and post-anneal four-circle pole figure reflection geometry measurements. Full pole figures
were taken to determine the distribution of C54 TiSi2 grain orientations in narrow (0.2 to 1.1 μm) lines which was compared with similar results obtained from unpatterned (blanket)
films. While in blanket films we found the presence of weak <311> C54 TiSi2 crystallographic orientation perpendicular to the sample surface, the <040> preferential orientation dominated in patterned
submicron line structures and increased with decreasing linewidth. Using pole figure analysis, we observed strong <040> fiber
texture in narrow lines with a slight variation in the tilt of the (040) planes normal in the direction perpendicular to the
line (full width at half maximum [FWHM] ≈6°), but very little along the length of the line (FWHM ≈2°). In addition, a preferred
in-plane (azimuthal) orientation of <040> crystals was found which showed that most of the <040> grains had their (004) plane
normals oriented parallel with the line direction. These findings support a model of the C49 to C54 TiSi2 transformation involving rapid growth of certain orientations favored by the one-dimensional geometry imposed by narrow lines. 相似文献
3.
Free-standing discontinuous Cu-line patterns varying in line widths and interline distances in the range of a few micrometers
were manufactured by combining photolithography and electrochemical deposition. Two principally different seed layers, polycrystalline
Au and X-ray amorphous Ni-P, were applied prior to electrodeposition of the Cu lines as well as continuous Cu films, which
were deposited as reference. The effect of the seed layer and the influence of the pattern design on surface topography and
morphology of the deposits were studied by means of light optical and scanning electron microscopy (SEM). The growth behavior
is related to the developing crystallographic texture of Cu-line patterns and continuous films, as determined from calculated
orientation distribution functions (ODFs) on the basis of X-ray diffraction (XRD) pole figure measurements. While strong crystallographic
textures of Cu lines on polycrystalline Au were observed with pattern-dependent differences to continuous films, almost no
preferred grain orientations develop both for Cu lines and corresponding continuous films deposited on amorphous Ni-P. 相似文献
4.
L. M. Ephrath 《Journal of Electronic Materials》1975,4(6):1207-1227
Adherent, polycrystalline silicon films were vacuum deposited onto titanium passivated steel alloy substrates at substrate
temperatures between 535 and 650°C and onto aluminum films at substrate temperatures between 480 and 520°C. Silicon films
deposited onto titanium layers are characterized by a sub-micron grain size and a preferential orientation of the <110> direction
perpendicular to the growth surface. Resistivities of ∿104 ohm-cm are measured for the undoped films. Silicon films deposited onto aluminum layers have a larger grain size, ∿5μm, a
columnar morphology and a preferential orientation of the <111> direction perpendicular to the growth surface. As-deposited
resistivities of ∿102 ohm-cm are measured for these films. Boron and phosphorus doped silicon films on titanium layers were annealed. The behavior
with annealing of the electrical properties of the films depended on which doping impurity was used. Silicon films on aluminum
were annealed to reduce lattice damage within the silicon grains and to dope the films with aluminum from the aluminum layer.
Resistivities of several ohm-cm were measured for the annealed films on aluminum. 相似文献
5.
Lucia Hartmann Kim Tremel Sureeporn Uttiya Edward Crossland Sabine Ludwigs Navaphun Kayunkid Christelle Vergnat Martin Brinkmann 《Advanced functional materials》2011,21(21):4047-4057
Highly oriented films of regioregular poly(3‐hexylthiophene) (P3HT) are prepared by two methods: mechanical rubbing and directional epitaxial crystallization. The structure, nanomorphology, and optical and charge‐transport properties of the oriented films are investigated by electron diffraction, high resolution transmission electron microscopy (HR‐TEM), absorption spectroscopy, and transistor field‐effect measurements. In rubbed films, P3HT chains align parallel to the rubbing direction and the crystalline domains orientation changes from preferential edge‐on to flat‐on orientation. The maximum in‐plane orientation probed by absorption spectroscopy is a function of the polymer molecular weight Mw; the lower the Mw, the higher the in‐plane orientation induced by rubbing. The anisotropy of field‐effect mobility measured parallel and perpendicular to the rubbing shows the same trend as the absorption. The Mw‐dependence of the orientation is explained in terms of chain folding and entanglement that prevent the reorientation and reorganization of the π‐stacked chains, especially when Mw ≥ 50 kDa. For comparison, P3HT films are oriented by directional epitaxial crystallization using a zone‐melting technique. Electron diffraction and HR‐TEM show that epitaxial and rubbed films differ in terms of intralamellar order within layers of π‐stacked chains. Comparison of UV‐vis absorption spectra for the different samples suggests that the vibronic structure is sensitive to intralamellar disorder. 相似文献
6.
运用郎缪尔-布尔吉特法在聚酰亚胺衬底上制备聚偏氟乙烯及三氟乙烯(P(VDF-TrFE))共聚物薄膜.不同厚度薄膜的X射线衍射结果表明,薄膜具有良好的结晶特性,取向为(110).运用波长范围为300~1300nm的椭圆偏振光谱仪对薄膜光学特性进行了表征;运用Cauchy模型对不同角度(θ=75°和85°)测得的Ψ和Δ数据进行了拟合.获得了P(VDF-TrFE)薄膜的光学参数n, k, α以及薄膜的厚度.另外对薄膜的铁电性质的测量,其剩余极化达到了6.3μC/cm2, 矫顽电场为100MV/cm.介电测量得到了薄膜两个明显的相变,铁电-介电相变以及β弛豫. 相似文献
7.
《Electron Device Letters, IEEE》1984,5(2):38-40
Lateral zone melting from a fast-scanning (5-30-cm/s) e-beam line source has been used to grow single-crystal films with an area limited only by the e-beam scan field. Electron backscattering contrast and etch pit techniques have been used to study the crystallographic orientation and the extent of single-crystal silicon film growth on thermal SiO2 -coated silicon (SOI) wafers. 相似文献
8.
The out-of-plane thermal expansion coefficient α⊥ of biphenyldianhydride-phenylenediamine (BPDA-PDA) polyimide thin film between 20 and 400°C has been measured using a laser
spot scanning interferometer. The α⊥ varies from 100 ppm/°C at 20°C to 400 ppm/°C at 400°C. As the result of highly anisotropic microstructure, the α⊥ is much larger than the in-plane thermal expansion coefficient α∥ and increases dramatically when the temperature exceeds the glass transition temperature (≈320°C). 相似文献
9.
A series of high dielectric material Er_2O_3 thin films with different thicknesses were deposited on p-type Si (100) substrate by pulse laser deposition at different temperatures. Phase structures of the films were determined by means of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Leakage current density was measured with an HP4142B semiconductor parameter analyzer. The XRD and HRTEM results reveal that Er_2O_3 thin films deposited below 400 ℃ are amorphous, while films deposited from 400 to 840 ℃ are well crystallized with (111)-preferential crystallographic orientation. I-V curves show that, for ultrathin crystalline Er_2O_3 films, the leakage current density increases by almost one order of magnitude from 6.20 × 10~(-5) to 6.56×10~(-4) A/cm~2, when the film thickness decreases by only 1.9 nm from 5.7 to 3.8 nm. However the leakage current density of ultrathin amorphous Er_2O_3 films with a thickness of 3.8 nm is only 1.73×10~(-5) A/cm~2. Finally, analysis of leakage current density showed that leakage of ultrathin Er_2O_3 films at high field is mainly caused by Fowler-Nordheim tunneling, and the large leakage of ultrathin crystalline Er_2O_3 films could arise from impurity defects at the grain boundary. 相似文献
10.
Kwang-Chon Kim Hyun Jae Kim Sang-Hee Suh M. Carmody S. Sivananthan Jin-Sang Kim 《Journal of Electronic Materials》2010,39(7):863-867
Single-crystalline CdTe(133) films have been grown by metalorganic chemical vapor deposition on Si(211) substrates. We studied
the effect of various growth parameters on the surface morphology and structural quality of CdTe films. Proper oxide removal
from the Si substrate is considered to be the principal factor that influences both the morphology and epitaxial quality of
the CdTe films. In order to obtain single-crystalline CdTe(133) films, a two-stage growth method was used, i.e., a low-temperature
buffer layer step and a high- temperature growth step. Even when the low-temperature buffer layer shows polycrystalline structure,
the overgrown layer shows single-crystalline structure. During the subsequent high-temperature growth, two-dimensional crystallites
grow faster than other, randomly distributed crystallites in the buffer layer. This is because the capturing of adatoms by
steps occurs more easily due to increased adatom mobility. From the viewpoint of crystallographic orientation, it is assumed
that the surface structure of Si(211) consists of (111) terrace and (100) step planes with an interplanar angle of 54.8°.
This surface structure may provide many preferable nucleation sites for adatoms compared with nominally flat Si(100) or (111)
surfaces. The surface morphology of the resulting films shows macroscopic rectangular-shaped terrace—step structures that
are considered to be a (111) terrace with two {112} step planes directed toward 〈110〉. 相似文献
11.
Douglas I. Kushner Ahmet Kusoglu Nikolas J. Podraza Michael A. Hickner 《Advanced functional materials》2019,29(37)
The effects of film thickness and substrate composition on the ionomer structure in porous electrodes are critical in understanding pathways toward developing higher performance electrochemical devices, including fuel cells and batteries. Insights are gained into the molecular and nanostructural orientation dependence for thin Nafion films (12–300 nm thick) on gold, platinum, and SiO2 model substrates. Molecular orientation is determined from the birefringence measured using spectroscopic ellipsometry, while the nanostructural orientation of the ionic domains is measured using grazing‐incidence small‐angle X‐ray scattering. Density functional theory calculations for the molecular polarizability of the Nafion backbone and side chain show complimentary contributions to the measured birefringence values for the material. Nafion films prepared on SiO2 substrates exhibit a nearly isotropic molecular and nanostructural orientation. Films on gold and platinum display parallel backbone orientations, relative to the substrate, with decreasing film thickness. However, a birefringence transition toward molecular isotropy is observed for 30 nm thick films on Au and Pt; while the ionic nanostructured domains continuously align parallel to the substrate. This apparent isotropic molecular orientation with increasing domain orientation highlights the difference between the backbone and side chain orientation, a key finding for elucidating transport in confined films at the interfaces. 相似文献
12.
Quantitative Photoelastic Characterization of Residual
Strains in Grains of Multicrystalline Silicon
Masayuki Fukuzawa Masayoshi Yamada Md. Rafiqul Islam Jun Chen Takashi Sekiguchi 《Journal of Electronic Materials》2010,39(6):700-703
The residual strain and its variation in multicrystalline Si substrates for solar cells have been quantitatively characterized.
The strain was evaluated from the absolute difference of refractive indices |Δn| and the principal direction ψ of strain-induced birefringence measured by scanning infrared polariscope, and the effective
photoelastic coefficients calculated numerically at each grain, the crystallographic orientation of which was determined by
the electron backscatter diffraction technique. It has been shown that the residual strain increases at grains with multitwin
boundaries and in the vicinity of small-angle grain boundaries, reaching the order of 10−4, corresponding to 10 MPa in terms of stress. 相似文献
13.
14.
Growth characteristics and physical properties of PbTe/BaF2 prepared under nonequilibrium conditions
S. V. Plyatsko 《Semiconductors》1998,32(3):231-234
PbTe/BaF2 films were grown under nonequilibrium conditions by laser-modulated epitaxy. The structural properties of the layers were investigated by x-ray crystallographic methods and scanning tunneling microscopy. It was established that the films obtained under nonequilibrium conditions on (III)BaF2 substrates are granular (d?250 Å) with (001) orientation. The electrophysical and photoelectric properties of the films depend on the technological conditions of growth and are determined by states at intergrain boundaries. 相似文献
15.
《Microelectronics Reliability》2014,54(9-10):1877-1882
The influence of the different liner material stacks Ti–N/Ti, Ta–N/Ta and Ta–N/Ru on the microstructure of 1 μm thick sputtered Cu films is examined prior to and after annealing. It is shown that the liner has an impact on the crystallographic orientation distribution of the Cu grains and seriously affects the defect density in the Cu films. The measured Cu resistivity shows a strong dependence on the microstrain. 相似文献
16.
S. K. Roy A. S. Vengurlekar V. T. Karulkar A. V. Joshi S. Chandrasekhar 《Journal of Electronic Materials》1987,16(4):211-217
Pyrolytic dissociation of silane on substrates heated by a cw Ar ion laser beam has been used to deposit polycrystalline silicon
thin films. The effects of parameters like laser beam irradiance (power density), dwell time, silane pressure on the silicon
deposition are studied. To understand the film growth kinetics, an approximate relationship amongst the film thickness and
some of the above parameters is deduced from general chemical thermodynamic considerations. The crystallographic texture of
the grown silicon film is studied as a function of laser power. It is found that the texture (preferred orientation) changes
from 〈110〉 at low power to 〈111〉 at higher power. Mixtures of silane and phosphine at different partial pressures are used
to obtain phosphorous doped polysilicon films. These films show a thermally activated conductivity σ = σ0 exp ( -E
a
/kT) with the activation energyE
a
depending on the phosphine partial pressure. 相似文献
17.
飞秒脉冲激光沉积Si基a轴择优取向的钛酸铋铁电薄膜 总被引:3,自引:3,他引:3
在钛酸铋(Bi4Ti3O12)薄膜的制备过程中容易获得晶粒c轴垂直于基片表面的薄膜,而压电和铁电存储器主要利用a轴的自发极化分量,因而制备a轴择优取向的Bi4Ti3O12铁电薄膜具有特别的意义。采用飞秒脉冲激光作用在钛酸铋陶瓷靶上,采用Si(111)作为衬底,制备了a轴择优取向的钛酸铋薄膜。采用X射线衍射(XRD)的薄膜附件和场发射扫描电镜(FSEM)研究了薄膜的结构和形貌;采用傅里叶红外光谱仪测量了室温(20℃)下在石英基片上沉积的样品的光学特性;室温下沉积的钛酸铋薄膜呈c轴择优取向,晶粒的平均大小为20 nm,其光学禁带宽度约为1.0 eV。在500℃沉积的钛酸铋薄膜呈a轴择优取向,晶粒大小在30~300 nm之间,薄膜的剩余极化强度Pr为15μC/cm2,矫顽力Er为48 kV/cm。 相似文献
18.
Daoli Zhang Yiping Huang Jianbing Zhang Lin Yuan Xiangshui Miao 《Journal of Electronic Materials》2011,40(4):459-465
ZnO nanopolycrystalline thin films were deposited by the sol–gel technique on glass and silicon, and compared systematically
via atomic force microscopy, scanning electron microscopy, x-ray diffraction, UV–Vis spectrophotometry, and fluorescence spectrophotometry.
The thickness of the ZnO films was measured by ellipsometric microscopy. A higher preheating temperature was needed to obtain
films with a strong preferential orientation. The optimal annealing temperatures for c-axis films on glass and silicon substrates were 525°C and 750°C, respectively. The relative intensity of the blue–green emission
peak tends to increase with the annealing temperature. When the film is annealed in N2, the transmittance of the film reduces while the intensity of the blue–green emission increases. 相似文献
19.
N. T. Bagraev L. E. Klyachkin A. M. Malyarenko A. A. Andronov S. V. Robozerov 《Semiconductors》1999,33(1):51-55
Ultrashallow p
+-n junctions fabricated in Si(111) are investigated by low-and intermediateenergy electron-beam probing of the surface region
in order to determine how the crystallographic orientation of the silicon films affects the mechanisms for nonequilibrium
diffusion of boron. A comparative study is made of p
+-n junctions made on both (111) and (100) silicon with regard to how the irradiation-induced conductivity depends on the energy
of the primary electron beam, and also its distribution with area. Using this method, it is possible to determine how the
probability of an electron-hole pair being separated by the electric field of the Si(111) and Si(100) p
+-n junctions varies with depth into the crystal, which experiments show is different, depending on whether diffusive motion
of impurities is dominated by the kick-out or dissociative-vacancy mechanisms. It was found that for boron in silicon the
kick-out type of diffusion mechanism is strongly enhanced in the [111] crystallographic direction, whereas diffusion in the
[100] direction is primarily driven by vacancy mechanisms. It is shown that collection of nonequilibrium carriers in the p
+-n junction field is strongly enhanced when the diffusion profile consists of certain combinations of longitudinal and transverse
quantum wells.
Fiz. Tekh. Poluprovodn. 33, 58–63 (January 1999) 相似文献
20.
Two-beam coupling and energy transfer occur, because of the birefrin-gent nature of the photorefractive grating formed by the two interfering beams. We report the observation of the enhanced two-beam coupling in the semi-insulation Cr-doped GaAs crystals at 1.15μm polarized beam from a CW He-Ne infrared laser under DC electric fields.We have measured the gain coefficients as a function of the applied DC electric field and the grating spacing. The optimum experimental crystallographic orientation in cubic photo-optic crystals with on applied field has been discussed. These measured results are close to the predicted theoretical values. 相似文献