Physical properties of sputtered amorphous Ge: The role of the deposition rate

The role of the deposition rate was studied on thin layers of amorphous germanium, prepared by cathode sputtering. Strong influence of this technological parameter on the density, electrical conductivity and optical absorption was found. The dependences observed are discussed in terms of the presence of voids, which influence the properties of a-Ge in their vicinity. The effect of argon and the traces of oxygen in argon is considered.We thank Dr. M. Rozsíval for testing our samples by the electron diffraction and Dr. B. Velický for his interest and helpful discussions.     

Effects of annealing on gap states in amorphous Si films

Annealing behaviors of the activation energy for electrical conduction, the optical gap, and the spin density in amorphous Si are investigated. It is found that the Fermi level shifts downwards with the decrease of the spin density, increasing the decay length of the wave function of localized state at the Fermi level. The downward shift of the Fermi level suggests that the localized states in the upper energy region in the gap are annealed out more easily than those in the lower one.     

Carrier transport of doped nanocrystalline Si formed by annealing of amorphous Si films at various temperatures

Phosphorus- and boron-doped hydrogenated amorphous silicon thin films were prepared by the plasma-enhanced chemical vapor deposition method. As-deposited samples were thermally annealed at various temperatures to get nanocrystalline Si with sizes around 10 nm. X-ray photoelectron spectroscopy measurements demonstrated the presence of boron and phosphorus in the doped films. It is found that the nanocrystallization occurs at around 600 °C for the B-doped films, while it is around 700-800 °C for the P-doped samples. For the P-doped samples, the dark conductivity decreases at first and then increases with the annealing temperature. While for the B-doped samples, the dark conductivity monotonously increases with increasing annealing temperature. As a result, the carrier transport properties of both P- and B-doped nanocrystalline Si films are dominated by the gradual activation of dopants in the films. The conductivity reaches 22.4 and 193 S cm⁻¹ for P- and B-doped sample after 1000 °C annealing.     

Physical properties of hydrogenated amorphous gallium arsenide

Summary The elemental composition and the optical properties of hydrogenated amorphous GaAs prepared by r.f. reactive sputtering at different hydrogen and argon pressure and substrate temperature have been determined. From the dependence of the absorption coefficient on photon energy the optical gap has been deduced according to the Tauc law. The data obtained for stoichiometric samples are compared with similar data obtained by different authors. The influence of various deposition parameters on stoichiometry and on the optical properties is briefly discussed.     

高温退火对非晶CNx薄膜场发射特性的影响

采用射频磁控溅射方法在纯N2气氛中沉积了非晶CNx薄膜样品,并在真空中退火至900 ℃.对高温退火引起的CNx薄膜化学成分、键合结构及其场发射特性方面的变化进行研究.用傅里叶变换红外光谱和x射线光电子能谱分析样品的内部成分及键合结构的变化,其中sp2键及薄膜中N的含量与薄膜的场发射特性密切相关.退火实验的结果表明高温退火可以导致CNx薄膜中N含量大量损失,并在薄膜中形成大量sp2键,这些化学成分及键合结构上的变化将直接影响CNx薄膜的场发射特性.与其他温度退火样品相比,750 ℃退火的样品具有最低的阈值电场,显示出较好的场发射特性.     

Optical properties of amorphous Si/SiO2superlattice

Amorphous Si/SiO₂(a-Si/SiO₂) superlattices have been fabricated by the magnetron sputtering technique. The superlattice with an Si layer thickness of 1.8 nm has been characterized by transmission electron microscopy (TEM). The result indicates that most of the regions in the Si layer consist of amorphous phase, while regular structure appears in some local regions. This is in agreement with the Raman scattering spectroscopy. The optical absorption spectrum and photoluminescence (PL) spectrum have been measured. Moreover, the third-order optical nonlinearity χ⁽³⁾of this superlattice has been measured. To our knowledge, this is the first investigation of the nonlinear absorption and refractive index of an a-Si/SiO₂superlattice using the Z -scan technique. The real and imaginary parts of χ⁽³⁾have been found to be 1.316  ×  10 ^− 7eus and  − 5.596  ×  10 ^− 7eus, respectively, which are about two orders of magnitude greater than those of porous silicon. The results may be attractive for potential application in electro-optics devices.     

Microstructural changes in amorphous Si/crystalline Al thin bilayer films upon annealing

Microstructural changes occurring in a sputter deposited Si (150 nm, amorphous)/Al (50 nm, crystalline); {111} fibre textured bilayer, upon annealing at 523 K for 60 min in a vacuum of 2.0×10^-4 Pa, were analyzed employing X-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, atomic force microscopy and focused-ion beam imaging. After the annealing the Al and Si sublayers had largely exchanged their locations in the bilayer; i.e. the Si layer was adjacent to the substrate after annealing. Simultaneously, the amorphous Si layer had crystallized into an aggregate of {111} oriented nanocrystals, with a crystallite size of about 15 nm. The Al layer, now adjacent to the surface, had formed a uniformly net-shaped layer in association with an increase of the surface roughness. Upon this rearrangement, the already initially present Al {111} fibre texture had become stronger, the Al crystallites had grown laterally and the macrostress in the Al layer had relaxed. An extensive analysis of thermodynamic driving forces for the transformation indicated that the largest gain in energy upon transformation is due to the crystallization of the amorphous Si. The only identifiable driving force for the layer exchange appears to be the release of elastic energy upon the rearrangement of the Si and Al phases in the layer. PACS 61.43.D; 61.72.C; 62.40; 65.70; 68.55.J; 68.60.BThis revised version was published online in September 2004. Due to technical problems the PDF of the previous version was incomplete.     

高温退火对非晶CNx薄膜场发射特性的影响

采用射频磁控溅射方法在纯N₂气氛中沉积了非晶CN_x薄膜样品，并 在真空中退火至900 ℃.对高温退火引起的CN_x薄膜化学成分、键合结构及其场发射特性方面的变 化进行研究.用傅里叶变换红外光谱和x射线光电子能谱分析样品的内部成分及键合结构的变化，其中sp²键及薄膜中N的含量与薄膜的场发射特性密切相关.退火实验的结果表明 高温退火可以导致CN_x薄膜中N含量大量损失，并在薄膜中形成大量sp^{2< 关键词： x薄膜')" href="#">CN_x薄膜 化学键合 退火温度 场致电子发射}     

The influence of composition and field annealing on magnetic properties of FeCo-based amorphous and nanocrystalline alloys

We report the influence of composition and very high transverse field annealing on the magnetic properties and structure of four FeCo-based amorphous and nanocrystalline alloys. The compositions (Fe₅₀Co₅₀)₈₉Zr₇B₄ and (Fe₆₅Co₃₅)₈₉Zr₇B₄ were investigated changing the Fe:Co ratio from 50:50 to 65:35. (Fe₅₀Co₅₀)₈₅Zr₂Nb₄B_8.5 was chosen to investigate Nb substitution for Zr in an FeCo-based alloy. This substitution is shown to increase the magnetostrictive constant, _λS${\lambda }_{\mathrm{S}}$, of the nanocrystalline alloy from 36×10⁻⁶ to 54×10⁻⁶. The composition (Fe₆₅Co₃₅)₈₄Cr₅Zr₇B₄ was studied to investigate the influence of Cr on intergranular coupling across the amorphous matrix. Samples of each composition were annealed in the amorphous state at 300 °C and in the nanocrystalline state at 600 °C. Field annealing was performed in 17 T transverse field in an inert atmosphere. Frequency-dependent magnetic properties were measured with an automatic recording hysteresisgraph. Static magnetic properties were measured with a vibrating sample magnetometer. The mass-specific power loss of the alloys decreased with field annealing in both the nanocrystalline and amorphous states for some frequency and induction combinations. Furthermore, the hysteresis loops are sheared after field annealing, indicating a transverse magnetic anisotropy. The nanocrystalline (Fe₅₀Co₅₀)₈₅Zr₂Nb₄B_8.5 composition has a lower relative permeability than the other compositions.     

New insight into the optical properties of amorphous Ge and Si

A short range disorder model, unlike present long range disorder theories, has been able to account well for both the density of states and the optical properties of amorphous Ge and Si. Our results indicate that the imaginary part of the dielectric function for amorphous Ge and Si has the same form as an averaged gradient matrix element as a function of energy. This conclusion should be valid for all tetrahedrally bonded amorphous solids.     

Effect of annealing treatments on the microwave electromagnetic properties of amorphous FeCuNbSiB microwires

The amorphous FeCuNbSiB microwires are fabricated by using the melt extraction method and annealed separately at temperatures T = 573, 673, 723 and 773K for 1h. The effect of annealing treatment on the microwave electromagnetic properties of FeCuNbSiB wires/wax composites has been investigated for the first time. It is found that in a frequency range of 0.5--4.0GHz, the complex permittivity, permeability, magnetic and electric loss tangents of FeCuNbSiB wires/wax composites are strongly dependent on the annealing temperature and frequency. For T = 573, 723 and 773K, two resonance peaks are found at frequency f = 1.2 and 3.3GHz. However, for T = 673K, only one resonance peak occurs at f = 3.3GHz. The resonance peak at f = 1.2GHz is believed to be due to the stress-induced anisotropy, while the resonance peak at f = 3.3GHz is attributed to the random anisotropy.     

用模拟退火算法研究非晶硅薄膜的光学性质

在玻璃衬底上采用等离子体增强的化学气相沉积(PECVD)法制备了非晶硅薄膜(A-Si:H)。用紫外-可见-近红外分光光度计测出了其透射光谱。采用模拟退火算法研究了透射光谱,得出了薄膜的厚度、折射率和吸收系数随波长变化的关系式、光学带隙等光学常数,并对该方法的优缺点进行了讨论。     

MBE-grown Si: Er light-emitting structures: Effect of implantation and annealing on the luminescence properties

Features appearing in the photo-and electroluminescence spectra of light-emitting structures based on MBE-grown Si: Er layers are studied. The luminescence properties of Si layers implanted by Er and O ions were used as a reference. The temperature quenching of the photoluminescence intensity of Er-containing centers in MBE-grown and implanted layers can be approximated adequately by the same functional relationships with equal activation energies but with preexponential factors differing by more than two orders of magnitude. It is shown that the electroluminescence of Er³⁺ ions can be increased by additional coimplantation of erbium and oxygen ions into MBE-grown light-emitting diode structures and subsequent annealing. After this treatment, the Er-containing centers continue to dominate the luminescence spectrum.     

Rapid annealing of Fe-Si-B amorphous tapes by joule heating: Effects on magnetic and mechanical properties

We report a systematic study of relaxation effects in Fe-Si-B amorphous tapes rapidly annealed for short time at T≈800 K by Joule heating. It is found that this type of annealing in air can result in nearly the same degree of relaxation as obtained by two hours of conventional relaxation annealing in a furnace under inert gas or vacuum. The extent of relaxation as a function of current density and duration has been assessed by high precision calorimetric measurements and found to be highly reproducible. The effect of such rapid annealing on magnetic and mechanical properties are compared to those of conventional relaxation annealing for two hours at 655 K and found to be advantageous.     

Nonthermal pulsed laser annealing of Si; plasma annealing

In the accompanying paper we have given evidence that pulsed laser annealing of Si does not involve normal thermal melting and recrystallization. Here we argue the importance of the electron-hole plasma produced by the laser to the annealing process.     

Formation of near stoichiometric A15Nb3Si from annealing an amorphous alloy under high pressure

The A15Nb₃Si with a composition closed to stoichiometric compound has been synthesized under high pressure from a starting material of Nb₇₇Si₂₃ amorphous alloys. High pressure annealing was carried out in Bridgman anvils apparatus. The amorphous alloy would decompose into A15Nb₃Si, bcc Nb solid solution and hexagonal phase when it was annealed under a pressure lower or a temperature higher than that for forming single phase A15Nb₃Si. The yielded A15Nb₃Si exhibited a superconducting transition temperatureT _c of 19.1 K, and has been indexed unambiguously with a lattice parameter ofa=0.5093 nm. Moreover, a nonlinear relationship betweenT _c anda has been constructed from our experimental data, and aT _c of 27 K for stoichiometric A15Nb₃Si can be expected.     

Ultrashort laser-pulse annealing of hydrogenated amorphous silicon

Crystallization of hydrogenated amorphous silicon (a-SI:H) has been initiated using ultrashort laser-pulse train annealing. Optical microscopy, infrared absorption, Raman spectroscopy and photoluminescence measurements show that in our experiment the crystallized layer is localized on the surface and is non-epitaxial. The depth of the crystalline layer and its surface morphology are discussed. A sharp luminescence band at 0.970 eV with fine structure is found after laser annealing and is identified as a recombination center similar to irradiation induced defects in crystalline Si.     

Physical properties of vacuum evaporated CdTe thin films with post-deposition thermal annealing

This paper presents the physical properties of vacuum evaporated CdTe thin films with post-deposition thermal annealing. The thin films of thickness 500 nm were grown on glass and indium tin oxide (ITO) coated glass substrates employing thermal vacuum evaporation technique followed by post-deposition thermal annealing at temperature 450 °C. These films were subjected to the X-ray diffraction (XRD),UV-Vis spectrophotometer, source meter and atomic force microscopy (AFM) for structural, optical, electrical and surface morphological analysis respectively. The X-ray diffraction patterns reveal that the films have zinc-blende structure of single cubic phase with preferred orientation (111) and polycrystalline in nature. The crystallographic and optical parameters are calculated and discussed in brief. The optical band gap is found to be 1.62 eV and 1.52 eV for as-grown and annealed films respectively. The I–V characteristics show that the conductivity is decreased for annealed thin films. The AFM studies reveal that the surface roughness is observed to be increased for thermally annealed films.