ICMCTF1998 Session FP: F - Posters

The Cr-Si-O material system is of interest for use as a thin film resistor. Films are magnetron sputtered onto conducting substrates from metal-oxide compacts using an argon-oxygen working gas mixture. Film compositions that range from 50 to 100 vol.% SiO₂ are determined from elemental measurements of Cr, Si and O using Rutherford backscattering. A broad range of resistivities from 10¹ to 10¹⁴ Ohm-cm is found as measured through the 3000Å film thickness. An apparent anomalous behavior is found for the variation of resistivity with elemental Cr, Si and O composition. The anomaly can be interpreted as a discontinuous variation of resistivity for film compositions above 80 vol.% SiO₂. The film microstructure is characterized using electron microscopy as a distribution of conducting metal-silicide particles within an insulating matrix. The variation of conductivity with volume percent metal for metal particle - insulator systems can be modelled in terms of an "effective medium" theory. This theory is now used to predictively model the Cr-Si-O resistivity behavior.

This work was performed under the auspices of the United States Department of Energy by Lawrence Livermore National Laboratory under contract #W-7405-Eng-48.

The post-implantation damage was produced by energetic 100 KeV Ar⁺ ions at different doses in Ge epitaxial layer grown on Si wafer.

This damage was independently assessed by RBS/channeling and X-ray diffraction (XDR) methods, and an analytical relation between two methods was derived.

It was shown by XRD that an amorphization of the damaged epitaxial layer is reached at much higher irradiation dose than it was estimated trough RBS/channeling measurements.

A mathematical model is presented for a thin piezoelectric film sputtered onto a substrate. The film is modeled as a network of springs and nodes and the substrate determines the boundary conditions at the interface. Springnode models (SNM) have been used to model local phenomena, like stress concentrations at crack tips, stress intensity factors and dynamic crack growth. However, the spring layout of existing models have restricted their application to isotropic materials with specific ratios of Lame constants. One feature of SNM which is particularly attractive, is the ease with which the model can inclue the effect of existing cracks on the stress distribution and the formation of new cracks, albeit in a qualitative sense.

In this work the model is generalized to describe not only general isotropic materials, but also anisotropic ones. The spring constants are selected so that a Taylor expanision of the equations match the constitutive equations of the continuum description and the model can now be employed to study piezoelectric materials. In this work the response of a ZnO film to mechanical perturbations is modeled. These results are compared with a film that has a distribution of fine cracks.

In the latter case, the waves are scattered and the cracks also act as focusing points for the potential distribution. These models provide insightful information on the aging effects as well as the performance of piezoelectrics under loading that could lead to local cracking.

The thermal conditions at the substrate surface influence essentially the elementary processes (adsorption, diffusion, desorption) as well as the structure and composition of the surface layers during deposition of thin metal and metal-oxide films. Besides an external heating or cooling, respectively, the energy balance of a substrate is determined by the plasma process itself.

The integral energy influx during sputtering mainly consits of the kinetic energy of charge carriers and sputtered particles, and the released condensation heath. By variation of the substrate potential the contribution of ions and electrons could be separated. The electron density was measeured by Langmuir-probes and self-excited electron resonance spectroscopy. The contribution of the electrons has been calculated for different energy distributions, too. The influence of the ions as well as of the sputtered particles on the energy balance was studied by energy-resolved mass spectrometry. The contributions of both components could be distinguished by variation of the potentials and the distance between target and substrate.

The measured intergral energy influx which has been determined from the raise of the surface temperature at the sputtering process is in good accordance with the proposed model.

The semiconducting alloys of bismuth antimony tellurid are the best materials currently available for thermoelectric applications near room temperature. Increasing interest in thin film thermoelectrtic devices stimulates the study on (Bi _1-x Sb _x) ₂ Te ₃ alloy thin films. In this paper the electrical conduction studies on (Bi _0.5 Sb _0.5 ) ₂ Te ₃ alloy films are presented. These films have been prepared by the flash evaporation method on clean glass plates in a vacuum of 1 x 10 ^-5 torr. The thickness of the films was monitored by a quartz crystal thickness monitor. The rate of deposition was also controlled to 10 a+- 1 ao A. As using the quartz crystal thickness monitor. Electrical resistance measurement was carried out in a vacuum of 1 x 10 ^-5 torr.

The structural analysis, which was carried out by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) techniques revealed that all the films were polycrystalline with hexagonal structure. The compositional analysis was carried out by Energy Dispersive Analysis by X-rays (EDAX). From, the resistance vs temperature plots for as-grown and annealed films of thickness 1000 ao A, it is observed that resistance variation during the heating cycle of the as-grown film is entirely different from that in the cooling cycle. But the resistance variation in the heating and cooling cycles of the annealed films is the same. This indicates that during heating of the as-grown films most of the frozen in non-equilibrium defects are annealed out. The plots of in (σ) vs 1000/T for the films of two different thicknesses are near-linear which indicates that these films are semiconducting. The activation energy of the films is calculated to be 55 meV and 50 meV for the films of thickness 1000 ao A and 2000 ao A respectively. It is also found that the resistivity of the films is dependent on the film thickness and the thicker film has a low resistivity value while the thinner film has a high resistivity value. This variation of resistivity with thickness is due to the classical size effect.

The electrical properties of ferroelectric devices are mainly depended on the microstructure of ferroelectric film and the interfacial state with electrodes. Concerning with the interface, the formation of depletion region is a dominant cause to degrade the electrical properties. Even though a lot of works have been done on the relationship between depletion region and the electrical property, but there is no clean explanation on the origin of the depletion region. And the suppressing methodology to the formation of depletion region was not given for the amelioration of ferroelectric properties.

In this work, PZT thin film was deposited on the Pt and RuO₂ electrode by RF-magnetron sputtering system. For the investigation of excess lead and oxygen role to the formation of depletion region, various PZT targets containing 10, 30, 50, and 100% of excess PbO contents were used. The phase and composition analyses using X-ray diffractometer, Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy and interfacial analysis of PZT/Pt and PZT/RuO₂ using angle-resolved XPS were performed . From the analyses, we observed that non-perovskite α - PbO₂ phase in as-deposited PZT film decomposes and compensates the Pb and O losses at near interface region during the inevitable post-anneal process. And the improvement of fatigue property after post-anneal depending on the excess contents of PbO was observed. From the above results, the degradation of electrical property of ferroelectric film is explained and the optimum preparative condition could be given.

For the development of compound semiconductor technology, passivation of the surface to stabilize it during the device process is a crucial issue. It has been announced that the improvement of electronic properties of GaAs device is obtained by passivating the surface with chalcogen atoms such as S and Se. However the nature of S or Se passivating the GaAs surfaces was not same and the characterization of the passivated surface structure on an atomic scale was urgently needed.

In this work, we performed the study on the structure of S and/or Se passivated GaAs surfaces using angle resolved X-ray photoelectron spectroscopy (ARXPS), low energy electron diffraction (LEED), and ion scattering spectroscopy (ISS). S and Se passivations of GaAs has been done using (NH₄)₂S_x, (NH₄)₂S+Se, and Na₂Se/NH₄OH solutions, respectively. The passivated GaAs surface structures were estimated with layer attenuation model from ARXPS results by varying the take-off angle. Photoemission studies showed that the surface is terminated with about a monolayer of sulfur and selenium. LEED patterns showed the regular distribution of passivating species on the S and Se terminated surfaces. ISS was used to confirm the distributional model for passivated surfaces. Through the above analyses, acceptable structural models were proposed for S and/or Se treated GaAs surfaces.