摘要:

Theoretical calculations are developed in the present study in order to predict propagation characteristics of surface transverse waves (STW) on piezoelectric substrates. A general model has been implemented for both cases of shallow groove or thin metal strip grating resonators. The analysis gives access to the principal STW characteristics (propagation and attenuation coefficients, velocity, electrical and mechanical amplitudes) and the dispersion curve relating the angular frequency to the propagation coefficient. The results obtained are in good agreement with previous results without piezoelectricity. Improvements on theoretical predictions are emphasized for the case of STW propagating under thin metal strips on AT‐cut quartz. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359590

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In this study a ferroelectric liquid crystal (FLC) monoacrylate (S)‐4‐(1‐ethoxycarbonyl‐1‐ethyloxy)phenyl 4’‐(11‐acryloyloxyundecyloxy)biphenyl‐4‐carboxylate was used. Room‐temperature spontaneous polarization of the monoacrylate was measured to be 190 nC/cm2. The monoacrylate was provided with 10% LC diacrylate. After inducing macroscopic molecular and dipolar orientation in the ferroelectric phase, polymerization within the reactive system was induced photochemically. In this way an anisotropic polymer network with a spontaneous polarization was produced. Within this network the crosslinks were formed by the diacrylate molecules. The anisotropic network was transparent and highly birefringent. The system showed high thermal stability and remained anisotropic even after being heated to elevated temperatures. The presence of dipolar orientation within the anisotropic networks was characterized by piezoelectric measurements. The piezoelectric coefficient within these networks was found to be highly dependent on the direction of the applied strain. The highest value was measured in the direction perpendicular to the molecular orientation and was 29 pC/N. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359153

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The diffusion of platinum in thin copper films has been studied by Rutherford backscattering spectrometry (RBS) under the kinetic conditionsB(within the temperature range of 200–290 °C) andC(room temperature). The RBS spectra were modified to concentration curves for both bulk and grain boundary (GB) diffusion. Under the kinetic regimeBthe triple productsK&dgr;Db(Dbis the GB diffusion coefficient, &dgr; is the GB width,Kis the enrichment ratio) were obtained using Whipple’s model. Under the kinetic regimeCthe absolute value of the GB diffusion coefficient of Pt in Cu films was obtained. A comparison between the data on GB diffusion for the kineticsBextrapolated to room temperature and the data on GB diffusion for the kineticsCenables one to derive the productK&dgr; and to separate the contribution of segregation into the GB diffusion of Pt in Cu films. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359154

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new technology for self‐aligned Si‐Zn diffusion into GaAs and AlGaAs is described. In this technology, closed‐tube Si diffusion is obtained from a sputtered SiNxfilm, and Zn diffusion self‐aligned to the Si diffusion window is obtained by reusing the SiNxfilm as the mask. The key to a successful self‐aligned Si‐Zn diffusion is that the SiNxfilm is controlled to have a proper refractive index profile. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359155

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This article experimentally identifies the hydrogen incorporation and release processes which control the final hydrogen content of hydrogenated amorphous silicon films (a‐Si:H). We deposit films using reactive magnetron sputtering of a silicon target in an Ar and H2atmosphere. Hydrogen incorporation or loss is measured using real time infrared reflectance spectroscopy. An optical cavity substrate increases the sensitivity, allowing us to observe Si–H bonding in layers ≥5 A˚ thick via the stretching mode absorption (1800–2300 cm−1). We observe a narrow component at ∼2100 cm−1corresponding to all SiHxbonds on the physical surface; the line width allows us to distinguish this contribution from the broader bulk modes. Various combinations of growth flux (isotope labeling, hydrogen partial pressure between 0.1 and 2.0 mTorr) and substrate material (on SiO2,a‐Si, ora‐Si:D) at substrate temperatures between 120 and 350 °C are used to distinguish various mechanisms. From the deposition ofa‐Si:H films on SiO2, we quantify the H surface coverage at the end of the nucleation stage (10 A˚ of growth) to be 1.2±0.3×1015cm−2, essentially independent of growth conditions. From the evolution of Si–H bonding during the initial growth (≤25 A˚), we infer a reduction of the surface area (smoothening) during nucleation and coalescence. Duringa‐Si:H growth on unhydrogenateda‐Si, we observe H implantation up to a depth of 40 A˚, and derive the total flux of arriving H as a function of hydrogen partial pressure. For the exposure ofa‐Si:H to atomic deuterium and ofa‐Si:D to atomic H, we observe a loss/gain of surface H due to abstraction or exchange reactions. Whena‐Si:D ora‐Si films are deposited ona‐Si:H films, we observe H loss from the bulk of the film due to fast particle bombardment at the growing surface. Based on the experimental evidence, we discuss the dependence of various H incorporation and release processes on the incident H flux, substrate temperature, and deposition rate. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359156

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Metal‐vapor vacuum arc ion source was employed to synthesize Ti silicides by Ti implantation directly into Si or through a deposited titanium film on Si wafers. The implantation was conducted at room temperature at an extracted voltage of 40 kV. In the directly implanted Si wafers, the transition of Ti disilicides from a metastable C49‐TiSi2to an equilibrium phase C54‐TiSi2was observed when the current density was of 125 &mgr;A/cm2at a nominal dose range of 3–5×1017/cm2, while in the Si wafers with a deposited Ti film, C54‐TiSi2was formed when the current density was of 125 &mgr;A/cm2at a fixed nominal dose of 5×1017/cm2. The temperature rise caused by ion implantation was calculated by solving a differential thermal conduction equation and the results were employed to discuss the formation mechanism of Ti silicides. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359157

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A detailed double crystal x‐ray diffractometry study of epitaxial AlN thin films grown on sapphire, silicon and silicon carbide substrates was carried out to compare the structure, residual stress and defect concentration in these thin films. The structure of AlN is wurtzite with a small distortion in lattice parameters. This results in a small residual stress of the order of 109dynes/cm2in the film and can be accounted for from the difference in thermal expansion coefficients between the film and substrate. Both the x‐ray and transmission electron microscopy measurements indicate a low defect density in the AlN thin film grown on 6H‐SiC substrate which could be attributed to the small difference in lattice parameters between AlN and 6H‐SiC. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359158

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The growth of diamond films by sequentially exposing a heated silicon substrate to fluxes of carbon, atomic hydrogen, and atomic oxygen is reported on. High quality diamond films can be grown sequentially using only the hydrogen and carbon sources. Here the use of an additional source of atomic oxygen is reported on. Film growth for both the possible exposure sequences to the three sources has been attempted. No film is grown if the exposure sequence is carbon‐oxygen‐hydrogen. When the exposure sequence is carbon‐hydrogen‐oxygen it is found that the flux of hydrogen necessary for the growth of high quality diamond films is less than that for runs in which no oxygen is present. The growth rate of diamond is also enhanced up to 500% with atomic oxygen. The role of atomic oxygen in modifying the growth surface is discussed to explain the improvement of growth rate and quality of these films. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359093

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Diamond films are becoming more prevalent for application in microelectronic devices, tool bits, and optical coatings because of diamond’s hardness and high thermal conductivity. Growth of these thin films on existing thin film/substrate structures occurs at temperatures high enough to induce structural relaxation in substrates with low melting points, such as germanium. Such relaxation affects the stress of the depositing film. A numerical model of film growth of one film on a multilayered structure that relaxes has been developed. Results show that significant tensile stresses in the depositing film arise during the deposition process, even though the end resulting stress is compressive. With faster deposition rates, the magnitude of this tensile stress is reduced. Further analysis suggests that allowing the substrate to relax initially before the deposition process begins is beneficial to avoid harmful tensile stresses. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359094

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This paper describes experimental results on low frequency noise in several types of polysilicon‐emitter NPN bipolar junction transistors. The experimental data were modelled using a combination of 1/fnoise, generation‐recombination noise (g‐r), and shot noise, and good agreement between model calculations and experimental measurements were obtained. Observed differences in the experimental low frequency noise spectra of devices with similar geometry and under similar biasing conditions could be explained by the differences in the generation‐recombination (g‐r) noise contributions. Experiments were performed on devices with emitter areas varying from 1.6 to 144 &mgr;m2, and it was found that the magnitude of the flicker noise contributionKFvaried inversely with emitter areaAEor emitter perimeterPE. The fact thatKF∼A−1EorKF∼P−1Eis explained by the observation thatAE∼PEwithin fabrication errors/tolerances. Using a set of 3.2 &mgr;m2BJTs with pronounced g‐r noise, input current noise was measured at different temperatures and from a deconvolution of the noise spectra, a trap at ∼400 meV and with a capture cross section of ∼4×10−17cm2was identified. Finally, the effect of different base implant and rapid thermal annealing conditions, polysilicon emitter thicknesses, and surface etching conditions on the noise magnitude were studied, and these results are also reported. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359095

出版商:AIP    

年代:1995

数据来源: AIP