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1.
β-FeSi2 thin films were prepared on Si (1 1 1) substrates by pulsed laser deposition (PLD) with a sintering FeSi2 target and an electrolytic Fe target. The thin films without micron-size droplets were prepared using the electrolytic Fe target; however, the surface without droplets was remarkably rougher using the Fe target than using the FeSi2 target. After deposition at 600 °C and then annealing at 900 °C for 20 h, XRD indicated that the thin film prepared using the Fe target had a poly-axis-orientation, but that prepared using the FeSi2 target had a one-axis-orientation. The PL spectra of the thin films prepared using the FeSi2 and Fe targets at a growth temperature of 600 °C and subsequently annealed at 900 °C for 20 h had A-, B- and C-bands. Moreover, it was found that the main peak at 0.808 eV (A-band) in the PL spectrum of the thin films prepared using the FeSi2 target was the intrinsic luminescence of β-FeSi2 from the dependence of PL peak energy on temperature and excitation power density. 相似文献
2.
β-FeSi2 thin films were prepared on FZ n-Si (1 1 1) substrates by pulsed laser deposition (PLD). The structural properties and crystallographic orientation of the films were investigated by X-ray diffraction (XRD) analysis. This indicates that β-FeSi2/Si (2 0 2/2 2 0) and the single-crystalline β-FeSi2 can be prepared using PLD. In photoluminescence (PL) measurements at 8 K detected by Ge detector, the PL spectra of the samples annealed at 900 °C for 1, 5, 8 and 20 h showed that the PL intensity of the A-band peak increased depending on annealing time in comparison with those of as-deposited samples. The intrinsic PL intensity of the A-band peak at 0.808 eV of the β-FeSi2 from the 20-h-annealed sample was investigated for the first time by the PLD method detected by an InGaAs detector. This result has been confirmed by temperature dependence and excitation power density of the 20-h-annealed sample with the comparison of other defect-related band peaks of the sample. Cross-sectional scanning electron microscopy (SEM) observation was also performed and the thickness of the thin films was found to be at 75 nm for 20-h-annealed. The thermal diffusion for the epitaxial growth of β−FeSi2/Si was observed when the compositional ratio of Fe to Si was around Fe:Si=1:2 for 20-h-annealed carried out by energy dispersive X-ray spectroscopy (EDX). We discussed high crystal quality of the epitaxial growth and optical characterization of β-FeSi2 achieved after annealing at 900 °C for 20 h. 相似文献
3.
F. Esaka H. Yamamoto Y. Yamada K. Yamaguchi M. Magara 《Applied Surface Science》2010,256(10):3155-3159
A combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is applied to clarify surface chemical states of β-FeSi2 films fabricated by an ion-beam sputtering deposition method. The differences in the chemical states of the films fabricated at substrate temperatures of 873, 973 and 1173 K are investigated. For the film fabricated at 873 K, Si 2p XPS spectra indicate the formation of a relatively thicker SiO2 layer. In addition, Fe L-edge XAS spectra exhibit the formation of FeSi2−X by preferential oxidation of Si or the presence of unreacted Fe. The results for the film fabricated at 1173 K imply the existence of FeSi2 with α and ? phases. In contrast, the results for the film fabricated at 973 K indicate the formation of relatively homogeneous β-FeSi2. These imply that the relatively excellent crystal property of the film fabricated at 973 K is due to the formation of homogeneous β-FeSi2. As a conclusion, the combination of XPS and XAS using synchrotron radiation is a powerful tool to elucidate the surface chemical states of thin films. 相似文献
4.
We have reported a one step growth of a high quality β-FeSi2 epitaxial film on hydrogen terminated Si(1 1 1) by using molecular beam epitaxy (MBE) without template layer or post-growth annealing. In the present work, the growth process was studied by analyzing X-ray diffraction (XRD) spectra, reflective high energy electron diffraction (RHEED) and atomic force microscopy (AFM) observations on the samples grown with different growth times from 10 s to 1 h. A phase transformation from γ-FeSi2 to β-FeSi2 was confirmed existing in the crystal film growth, as well as the growth mode changing from three-dimensional (3D) to two-dimensional (2D) mode. 相似文献
5.
We have investigated the growth of iron disilicide on Au-coated Si(0 0 1) substrates and its photoluminescence behaviour. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy observations revealed that the Si surface above 380 °C was melted as a result of the Au-Si eutectic reaction and that coarse island disilicide grains with sizes of several micrometres were formed on the Si surface. The full width at half maximum of 0.056° on the rocking curve of α-FeSi2004 was observed on the sample deposited at 800 °C, and indicated the high crystal quality in perfection of orientation. The photoluminescence spectrum of β-FeSi2 grains, which were deposited at 750 °C, was observed. The melted Si surface contributed to the improved crystallinity of α-FeSi2 and β-FeSi2. 相似文献
6.
(2 0 2)/(2 2 0)-oriented epitaxial β-FeSi2 thin films were deposited on textured Si (1 0 0) substrate by magnetron sputtering. The influences of thickness and annealing temperature on the β-FeSi2 crystallization were studied to find the optimal condition. The results of surface morphology and optical property measurements showed that the inverted pyramid array in the surface of β-FeSi2 thin films could reduce the surface reflection of β-FeSi2. In dark condition, the β-FeSi2/textured-Si heterojunction showed diode property with rectifying ratio of 2.89 × 105 and built-in potential of 0.58 V. These results indicated the potential application of textured Si substrate in β-FeSi2 solar cells. 相似文献
7.
The mechanism of improving 1064 nm, 12 ns laser-induced damage threshold (LIDT) of TiO2/SiO2 high reflectors (HR) prepared by electronic beam evaporation from 5.1 to 13.1 J/cm2 by thermal annealing is discussed. Through optical properties, structure and chemical composition analysis, it is found that the reduced atomic non-stoichiometric defects are the main reason of absorption decrease and LIDT rise after annealing. A remarkable increase of LIDT is found at 300 °C annealing. The refractive index and film inhomogeneity rise, physical thickness decrease, and film stress changes from compress stress to tensile stress due to the structure change during annealing. 相似文献
8.
Completely amorphous Fe-Si layers are formed by Fe implantation into Si substrate at a dosage of 5×1015 cm−2 using a metal vapor vacuum arc (MEVVA) ion source under 80 kV extraction voltage and cryogenic temperature. After thermal annealing, β-FeSi2 precipitates are formed in Si matrix. The influence of impurities in these amorphous Fe-Si layers on the photoluminescence (PL) from β-FeSi2 precipitates is investigated. PL is found to be significantly enhanced by optimizing the impurity concentration and annealing scheme. After 60 s of rapid thermal annealing (RTA) at 900 °C, β-FeSi2 precipitates in medium boron-doped Si substrate give the strongest PL intensity without boron out-diffusion from them. 相似文献
9.
Synthesis of ultrathin semiconducting iron silicide epilayers on Si(1 1 1) by high-temperature flash
I. Goldfarb 《Surface science》2004,554(1):L87
In this work ultrathin iron silicide epilayers were obtained by the reaction of iron contaminants with the Si(1 1 1) substrate atoms during high-temperature flash. After repeated flashing at about 1125 °C, reflection high-energy electron diffraction indicated silicide formation. Scanning tunneling microscopy revealed highly ordered surface superstructure interrupted, however, by a number of extended defects. Atomic-resolution bias-dependent imaging demonstrated a complex nature of this superstructure with double-hexagonal symmetry and (2√3×2√3)-R30° periodicity. Among the possible candidate phases, including metastable FeSi2 with a CaF2 structure and FeSi1+x with a CsCl structure, the best match of the interatomic distances to the measured 14.4 Å × 14.4 Å unit cell dimensions pointed to the hexagonal Fe2Si (Fe2Si prototype) high-temperature phase. The fact that this phase was obtained by an unusually high-temperature flash, and that neither its reconstruction nor its semiconducting band-gap of about 1.0 ± 0.2 eV (as deduced form the I-V curves obtained by scanning tunneling spectroscopy) has ever been reported, supports such identification. Due to its semiconducting properties, this phase may attract interest, perhaps as an alternative to β-FeSi2. 相似文献
10.
To explore the origin of low conversion efficiency for novel β-FeSi2/c-Si heterojunction solar cells, the effect of surface recombination and interface states on the cell performance has been investigated by numerical simulation. The present results show that surface recombination of β-FeSi2 film plays an important role in limiting the cell property since the photovoltaic behavior of β-FeSi2 is quite sensitive to surface recombination due to its especial characteristic of very high optical absorption coefficient. Surface quality of β-FeSi2 film should be much improved for better cell performance. In addition, it is shown that interface states between β-FeSi2 film and crystalline silicon are critical to device characterization. Interface states should be minimized to obtain higher conversion efficiency. If surface recombination and interface states can be best suppressed, potential conversion efficiency for the cell may be up to 28.12% at 300 K under illumination of AM 1.5, 100 mW/cm2. 相似文献
11.
采用射频磁控溅射的方法,在Si(100)基片上制备了纳米β-FeSi2/Si多层结构,利用X射线衍射、透射电子显微镜、光致发光光谱等表征技术,研究了β-FeSi2/Si多层结构的结构、成分和光致发光特性.研究结果表明:利用磁控溅射法得到的Fe/Si多层膜,室温下能够检测到β-FeSi2的1.53 μm处光致发光信号;未退火时多层膜是(非晶的FeSi2+β-FeSi2颗粒)/非晶Si结构,退火后则是
关键词:
2')" href="#">β-FeSi2
磁控溅射
XRD
光致发光光谱 相似文献
12.
Daoren Gong 《Applied Surface Science》2008,254(15):4875-4878
Single-phase semiconducting iron disilicide (β-FeSi2) films on silicon substrate were fabricated by electron beam evaporation (EBE) technique. For preventing the oxidation of Fe film, silicon/iron/silicon sandwich structure films with different thickness of silicon and iron were deposited and then annealed at different temperatures. X-ray diffraction (XRD), Raman and Fourier transform infrared spectroscopy (FTIR) measurements were carried out to study the phase distribution and crystal quality of the films. Single-phase β-FeSi2 with high crystal quality was achieved after annealing at 800 °C for 5 h. An apparent direct bandgap Eg of approximately 0.85-0.88 eV was observed in the β-FeSi2 films. It is considered that the silicon/iron/silicon sandwich structure is suited for formation of single-phase β-FeSi2 with high crystal quality. 相似文献
13.
HfO2 is one of the most important high refractive index materials for depositing high power optical mirrors. In this research, HfO2 thin films were prepared by dual-ion beam reactive sputtering method, and the laser-induced damage thresholds (LIDT) of the sample were measured in 1-on-1 mode for laser with 1064 nm wavelength. The results indicate that the LIDT of the as-grown sample is only 3.96 J/cm2, but it is increased to 8.98 J/cm2 after annealing under temperature of 200 °C in atmosphere. By measuring the laser weak absorption and SIMS of the samples, we deduced that substoichiometer is the main reason for the low LIDT of the as-grown sample, and the experiment results were well explained with the theory of electronic-avalanche ionization. 相似文献
14.
Electroluminescence (EL) properties of Si-based light emitting diodes with β-FeSi2 particles active region grown by reactive deposition epitaxy are investigated. EL intensity of β-FeSi2 particles versus excitation current densities has different behaviors at 8, 77 K and room temperature, respectively. The EL peak energy shifted from 0.81 to 0.83 eV at 77 K with the increase of current density from 1 to 70 A/cm2. Temperature dependence of the peak energy can be well fitted by semi-empirical Varshni's law with the parameters of α=4.34 e-4 eV/K and β=110 K. These results indicate that the EL emission originates from the band-to-band transition with the band gap energy of 0.824 eV at 0 K. 相似文献
15.
β-FeSi2-TiB2 composites with various amounts of TiB2, from 0 up to 30 vol%, were prepared by hot pressing. The electrical and thermal conductivities, and the Seebeck coefficient were measured as a function of temperature. The results show that the thermal and electrical transport behavior of the composites is different as the volume fraction of TiB2 is below and above about 0.255. A 5 vol% TiB2 added sample has higher figure of merit than one without TiB2 for temperatures above 650 K. The influence of an additional phase, ε-FeSi, formed during the hot pressing, on the thermoelectric properties of the β-FeSi2-TiB2 composites was also discussed. 相似文献
16.
H.Y. Chen X.B. Zhao T.J. Zhu C. Stiewe E. Mueller 《Journal of Physics and Chemistry of Solids》2008,69(8):2013-2018
The dynamic phase transformation and structure of rapidly solidified Fe1−xCoxSi2 (0.02?x?0.06) thermoelectric materials were in situ investigated under high temperatures and high pressures by energy dispersive X-ray diffraction using synchrotron radiation. The FeSi2 alloys which solidified as α-Fe2Si5 and ε-FeSi eutectic structures, were transformed to the semiconducting β-FeSi2 phase upon heating by the main reaction α+ε→β and the subsidiary reaction α→β+Si. The low heating rates and Co contents were found to be beneficial for the β phase formation. The decomposition temperature of β→α+ε was weakly dependent on heating rate, but significantly suppressed by the high pressures. 相似文献
17.
TiO2/SiO2 high reflectors with and without a SiO2 overcoat are deposited by electron-beam evaporation. The film properties are characterized by visible spectrometry measures, structure analysis, roughness and laser-induced damage threshold (LIDT) tests, surface defects and damage morphology observation. The effects of overcoats on LIDT at 532 nm, 8 ns and 800 nm, 220 ps laser pulses are investigated. The relations between film structure, roughness, surface defects, electric field and LIDT are discussed. It is found that overcoats can increase the LIDT at these two laser wavelengths. The reduction of peak temperature, the low defects density and roughness, the low intrinsic absorption of SiO2 and its amorphous structure are the main reasons for LIDT improvement by overcoats. 相似文献
18.
Meiqiong Zhan Hongbo He Yuanan Zhao Guanglei Tian Jianda Shao Zhengxiu Fan 《Applied Surface Science》2006,252(6):2126-2130
A series of HR coatings, with and without overcoat, were prepared by electron beam evaporation using the same deposition process. The laser-induced damage threshold (LIDT) was measured by a 355 nm Nd:YAG laser with a pulse width of 8 ns. Damage morphologies of samples were observed by Leica-DMRXE Microscope. The stress was measured by viewing the substrate deformation before and after coatings deposition using an optical interferometer. Reflectance of the samples was measured by Lambda 900 Spectrometer. The theoretical results of electric field distributions of the samples were calculate by thin film design software (TFCalc). It was found that SiO2 overcoat had improved the LIDT greatly, while MgF2 overcoat had little effect on the LIDT because of its high stress in the HR coatings. The damage morphologies were different among HR coatings with and without overcoats. 相似文献
19.
F. Esaka H. YamamotoH. Udono N. MatsubayashiK. Yamaguchi S. ShamotoM. Magara T. Kimura 《Applied Surface Science》2011,257(7):2950-2954
Chemical state analysis by a combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is performed for β-FeSi2 single crystals and homoepitaxial β-FeSi2 films. The Si 2p XPS and Fe L-edge XAS spectra imply that the annealing at 1173 K to remove native oxide layers on the crystal induces the formation of FeSi in the surface. The formation of FeSi is also confirmed by Si K-edge XAS analysis. For the homoepitaxial β-FeSi2 films grown on the crystals, the Si K-edge XAS spectra indicate that structurally homogeneous β-FeSi2 films can be grown on the β-FeSi2 single crystals when the substrate temperatures of 973 and 1073 K are applied for molecular beam epitaxy (MBE). Consequently, it is indicated that the combination of XPS and XAS using synchrotron radiation is a useful tool to clarify chemical states of β-FeSi2 single crystals and homoepitaxial β-FeSi2 films, which is important to reveal optimized growth conditions of homoepitaxial films. 相似文献
20.
For many applications, optical multimode fibers are used for the transmission of powerful laser radiation. High light throughput and damage resistance are desirable. Laser-induced breakdown at the end faces of fibers can limit their performance. Therefore, the determination of laser-induced damage thresholds (LIDT) at the surface of fibers is essential.Nanosecond (1064 nm and 532 nm wavelength) single-shot LIDT were measured according to the relevant standard on SiO2 glass preforms (Suprasil F300) as basic materials of the corresponding fibers. For 10 kinds of fused silica fibers (FiberTech) with core diameters between 180 μm and 600 μm, an illumination approach utilizing a stepwise increase of the laser fluence on a single spot was used. For both wavelengths, the LIDT values (0% damage probability) obtained by means of the two methods were compared. The influence of surface preparation (polishing) on damage resistance was investigated. For equal surface finishing, a correlation between drawing speed of the fibers and their surface LIDT values was found. In addition to the surface measurements, bulk LIDT were determined for the preform material. 相似文献