Auger study of Cr/Au thin films deposited on alumina and sapphire

R.f. sputtered Cr/Au films on alumina and sapphire substrates were subjected to thermal annealing treatments at 300 and 450 °C in vacuum and in air. These specimens were studied using Auger depth profiling and by measuring their sheet resistances. These results were analyzed and the Cr-Au interactions are described. At 300°C a grain boundary diffusion coefficient of 4X10^?15 cm²s^?1 for chromium in gold is derived.     

Thermal dewetting of thin Au films deposited onto line-patterned substrates

Au films are deposited onto line-patterned substrates, and the dewetting of the line-shaped films is studied. The results show that the line-patterned substrates can clearly lead to both, a decrease and an increase in the resulting particle size and particle spacing when compared to dewetting occurring on a flat substrate. The size and the spacing of the dewetted Au particles scale with the feature size of the line-shaped films in a Rayleigh-like way, but this scaling law ceases when the ratio of line width to film thickness reaches or exceeds a critical value.     

Optical properties of pulse laser deposited AlN thin films on silicon

Aluminium-nitride thin films were deposited on silicon Si(111) substrate with pulsed laser deposition in a Riber LDM-32 system. The optical properties of the films were studied by means of optical spectroscopy with an incoherent light source mainly covering the visible range. It is demonstrated that, in comparison with an aluminium mirror, under certain deposition conditions, the film may behave as a metallic thin film as far as the optical reflection is concerned. In this case, there is an enhanced plasmonic reflection peak in the optical spectrum and the peak may be modified according to the degree of the phase transition. The microscopic structures as well as the surface topographies of the films were also studied with X-ray photoelectron spectroscopy and scanning electron microscopy. It turns out that the density and the size of the microscopic domains in the film determine whether the film remains dielectric or becomes metallic. The diamagnetic effect in the enhanced plasma increases in the process when the sample is smoothed out with the optimized nitrogen gas pressure. The nitrogen pressure is thus identified as the most influential deposition condition to the phase transition.     

Growth and structure of polycrystalline Cr/Au multilayered thin films

Metallic multilayered thin films have recently been investigated due to their new magnetic and transport properties. The interest here is focussed on the characterization of the interfaces between the layers. The analysis of growth and structure of polycrystalline Cr/Au multilayers is accomplished by two complementary techniques: in situ ultrahigh vacuum scanning tunnelling microscopy and ex situ transmission electron microscopy. The combination of these powerful methods provides detailed information about structural characteristics such as crystallite size, surface roughness and crystallographic orientation. Moreover, conclusions can be drawn on the atomic arrangement and growth mechanism at the Cr-Au interface. The results are supported by semiempirical and theoretical expectations.     

Characterization of low pressure chemically vapour- deposited thin silicon nitride films

Silicon nitride films prepared on silicon by low pressure chemical vapour deposition (LPCVD) were characterized by electrical measurements (current-voltage and capacitance-voltage), Auger electron spectroscopy (AES) and reflection high energy electron diffraction (RHEED). The contact current versus contact field characteristics were interpreted in terms of the Fowler-Nordheim tunnelling of holes from silicon into silicon nitride, with the field of charged traps and the effect of changing the triangular shape of the barrier under steady state conditions taken into account and on the assumption of a Poole-Frenkel detrapping mechanism. AES data show that the LPCVD process yields stoichiometric Si₃N₄ films. RHEED data shows that films of thickness more than 10 nm are amorphous. Some crystalline structures of Si₃N₄ and SiO₂ are observed for thicknesses of less than 10 nm.     

VHF-PECVD沉积本征微晶硅薄膜氧污染研究

通过激活能测试装置测量VHF-PECVD高速沉积的本征微晶硅薄膜,并对不同沉积功率、不同沉积压强条件下沉积制备的样品的激活能进行了分析研究。结果表明:在不同功率、不同气压沉积条件下沉积的微晶硅薄膜,激活能偏低,薄膜在沉积过程中被氧杂质污染;随着沉积功率的增大和沉积气压的增大,沉积速率随着提高,样品的激活能升高,通过提高沉积功率和沉积气压可以有效的抑制氧污染。     

NH3 sensing characteristics of nano-WO3 thin films deposited on porous silicon

The NH3 sensing characteristics of nano-tungsten trioxide (WO3) thin films deposited on porous silicon (PS) were investigated in the present study. Porous silicon layer was first prepared by electrochemical etching in an HF-based solution on a p(+)-type silicon substrate. Then, WO3 nano-films were deposited on the porous silicon layer by DC magnetron sputtering. Pt electrodes were deposited on the top surface of the WO3 films to obtain the WO3/PS gas sensor. The WO3 films deposited on PS were characterized by SEM, XRD and XPS. The NH3 sensing characteristics for WO3/PS gas sensor were tested at room temperature and 50 degrees C. The results showed that the NH3 sensing characteristics of WO3/PS were superior to WO3/Al2O3 at room temperature. The sensing mechanism of the nano-WO3 thin films based on PS was also discussed.     

ECR-PECVD制备氮化硅薄膜的键态结构

用红外光谱和拉曼光谱分析了用低温电子回旋共振等离子体CVD技术制备的Si3N4薄膜的键态结构。结果表明Si3N4薄膜主要由Si-N键结构组成，还含有Si-H和Si-O-Si键结构。随着沉积温度的提高，Si3N4薄膜中的Si-H键减少，氢含量降低。可利用提高沉积温度来减少Si3N4薄膜中的氢含量。在沉积温度为420℃时Si3N4薄膜的Raman光谱在短波方向出现一新的展宽的拉曼散射峰。     

Nanoindentation stress-strain curves of plasma-enhanced chemical vapor deposited silicon oxide thin films

Plasma-enhanced chemical vapor deposited (PECVD) silicon oxide (SiO_x) thin films have been widely used in Micro/Nano Electro Mechanical Systems to form electrical and mechanical components. In this paper, we explore the use of nanoindentation techniques as a method of measuring equivalent stress-strain curves of the PECVD SiO_x thin films. Four indenter tips with different geometries were adopted in our experiments, enabling us to probe the elastic, elasto-plastic, and fully plastic deformation regimes of the PECVD SiO_x thin films. The initial yielding point (σ_I) and stationary yielding point (σ_II) are separately identified for the as-deposited and annealed PECVD SiO_x thin films, as well as a standard fused quartz sample. Based on the experimental results, a shear transformation zone based amorphous plasticity theory is applied to depict the plastic deformation mechanism in the PECVD SiO_x.     

X-ray determination of the residual stresses in thin aluminum films deposited on silicon substrates

Results of x-ray strees measurements on highly [111] textured thin aluminum films deposited on [100] silicon wafers were reported. Due to the texturing the conventional sin²ϕ technique for polycrystalline materials was found to be difficult to use. X-ray stress measurements were thus made as if the thin films were single crystals with [111] planes parallel to the substrate. The calculated stresses for unannealed specimens were found to be compressive and small, approximately -20 to -30 MPa. The calculated stresses for specimens annealed at 450°C were found, after a waiting time of 34 days, to be tensile and larger, approximately 120 to 140 MPa.     

Characterization of yttria-stabilized zirconia thin films deposited by electron beam evaporation on silicon substrates

Structure, phase composition and electrical conductivity of thin yttria-stabilized zirconia (YSZ) films deposited by electron beam evaporation on a silicon (1 0 0) substrate at different temperatures i.e. room temperature (r.t.), 700 and 830°C, as well as the quality of the YSZ–Si interface have been investigated. The phase composition was verified by Raman spectroscopy and by infrared (i.r.) transmission measurements. The structure of films changed in agreement with their electrical conductivity depending on the deposition temperature. Both structure and thereby electrical conductivity were influenced by the high concentration of Y2O3 stabilizer used and by the post-deposition thermal treatment of films. The deposition temperature was also important in determining the quality of the YSZ–Si interface and hence the accessible sweep of the surface potential. The capacitance–voltage characteristics of the metal–insulator–semiconductor (MIS) structures incorporating YSZ films measured at r.t. showed hysteresis and positive shifts of the flat-band voltages. © 1998 Chapman & Hall     

Residual stress in piezoelectric poly(vinylidene-fluoride-co-trifluoroethylene) thin films deposited on silicon substrates

The residual stress and its evolution with time in poly(vinylidene-fluoride-co-trifluoroethylene) (P(VDF-TrFE) (72/28)) piezoelectric polymer thin films deposited on silicon wafers were investigated using the wafer curvature method. Double-side polished silicon wafers with minimized initial wafer warpage were used to replace single-side polished silicon wafers to obtain significantly improved reliability for the measurement of the low residual stress in the P(VDF-TrFE) polymer thin films. Our measurement results showed that all the P(VDF-TrFE) films possessed a tensile residual stress, and the residual stress slowly decreased with time. Our analysis further indicates that the tensile stress could arise from the thermal mismatch between the P(VDF-TrFE) film and the silicon substrate. Besides possible viscoelastic creep mechanism in thermoplastic P(VDF-TrFE) films, microcracks with widths in the range of tens of nanometers appeared to release the tensile residual stress.     

Platinum thin films deposited on silicon oxide by focused ion beam: characterization and application

Focused ion beam system was used for deposition of platinum (Pt) thin films on thermally oxidized silicon (Si). Various test patterns (squares and lines) were deposited for electrical characterization of the films, using 2- and 4-terminal measurements. Tests with parallel Pt lines were also carried out, and considerable leakage was detected for the interline distances in the sub-micron range. We investigated two ways to decrease the leakage current: inducing surfaces roughness and using an oxygen plasma after patterns deposition. A method of dielectrophoresis with an AC electric field was applied to align and deposit metallic multi-wall carbon nanotubes (CNT) between pre-fabricated metal, gold, and palladium electrodes with a micron-scale separation. Further, using focused electron and ion beam-deposited Pt contacts in two different configurations (“Pt-on-CNT” and “CNT-on-Pt”), 4-terminal measurements have been performed to evaluate intrinsic nanotube resistances.     

Bulge testing and fracture properties of plasma-enhanced chemical vapor deposited silicon nitride thin films

The mechanical properties and fracture behavior of silicon nitride (SiN_x) thin film fabricated by plasma-enhanced chemical vapor deposition is reported. Plane-strain moduli, prestresses, and fracture strengths of silicon nitride thin films deposited both on a bare Si substrate and on a thermally oxidized Si substrate were extracted using bulge testing combined with a refined load-deflection model of long rectangular membranes. The plane-strain moduli and prestresses of SiN_x thin films have little dependence on the substrates, that is, for the bare Si substrate, they are 133 ± 19 GPa and 178 ± 22 MPa, respectively, while for the thermally oxidized substrate, they are 140 ± 26 GPa and 194 ± 34 MPa, respectively. However, the fracture strength values of SiN_x films grown on the two substrates are quite different, i.e., 1.53 ± 0.33 GPa and 3.08 ± 0.79 GPa for the bare Si substrate and the oxidized Si substrate, respectively. The reference stresses were computed by integrating the local stress of the membrane at the fracture over the edge, surface, and volume of the specimens and fitted with the Weibull distribution function. For SiN_x thin film produced on the bare Si substrate, the volume integration gave a significantly better agreement between data and model, implying that the volume flaws are the dominant fracture origin. For SiN_x thin film grown on the oxidized Si substrate, the fit quality of surface and edge integration was significantly better than the volume integration, and the dominant surface and edge flaws could be caused by buffered HF attacking the SiN_x layer during SiO₂ removal.     

Vacuum deposited polyimide thin films

Vacuum deposition as an attractive alternative for polyimide (PI) layers formation is discussed. PI thin films can be formed by vapour co-deposition of the precursor monomers pyromellitic dianhydride and 4,4′-oxydianiline following a thermal treatment at a temperature of over 150°C. The effects of the dynamic state of the substrate, dose stoichiometry and thermal treatment on the surface morphology and imidization rate of PI films were investigated using scanning electron microscopy, thermogravimetric, differential thermal analyses and Fourier transform infrared spectroscopy and microscopy. The results showed that the solid state reaction between the precursors starts at about 175°C. The imidization finishes in the temperature interval of 342–365°C. The destruction of PI is observed at 520°C. The surface morphology of the layers depends only on the monomer ratio. The resulting vacuum deposited PI films are smooth, uniformly thick and form without shrinkage.     

Low temperature photoluminescence and infrared dielectric functions of pulsed laser deposited ZnO thin films on silicon

C-axis oriented ZnO thin films were grown on silicon (100) and (111) substrates by pulsed laser deposition. Low temperature photoluminescence spectra show besides the peaks of free excitons, of defect bound excitons, and of a donor-acceptor pair transition a new doublet at 3.328/3.332 eV. The doublet seems to originate from the columnar textured ZnO film structure. A corresponding structural dependence of the broadening parameter of the infrared dielectric functions was derived from spectroscopic ellipsometry in the spectral range from 380 to 1200 cm^− 1. The wave numbers of the E₁ transverse optical and A₁ longitudinal optical phonon modes of the ZnO films on silicon are determined to be 406 and 573 cm^− 1, respectively. These values are slightly smaller than those of single-crystalline ZnO thin films on sapphire.