Structure Properties Of Thin Films Research Articles

Electrical and structural properties of thin films of sputtered CrSi2

Abstract Thin films of CrSi2 were deposited by r.f. sputtering from a CrSi2 target. The resistivity, the microstructure and the depth profiles of the films were measured with a four-point probe, a transmission electron microscope, and an Auger electron spectrometer. It is shown that the sputtered amorphous CrSi2 film crystallizes at 300 °C, reaching a higher resistivity state compared with that of the amorphous counterpart; the increase in resistivity is due to the formation of wide boundaries between columnar grains of the film after crystallization. A relatively stable resistivity state can be reached by annealing the film at a temperature between 375 °C and 425 °C.

Photovolatilization of thin polysilane films detected by surface-plasmon spectroscopy

Surface-plasmon optical techniques (attenuated total internal reflection and surface plasmon microscopy, in particular) are employed to characterize the optical and structural properties of thin films of poly(methyl-phenyl-silane) in the thickness range d0=40–400 nm. Irradiation with deep UV light (90% at λ=253.7 nm) is shown to cause photovolatilization which results in a self-development of illuminated areas. The time dependence of this etching process is investigated, and substantial differences between irradiation in air or in an Ar atmosphere of 10−3 MPa partial pressure are found: For 40-nm-thick films in the presence of oxygen an ablation rate of 1.3 nm/min is derived for the first 5–10 min which drops rather abruptly to zero (irradiation power density ∼0.4 mW/cm2 ). In Ar atmosphere the etching rate is ∼0.1 nm/min but constant for more than 1 h. UV-absorption spectra and gel permeation chromatography are performed to gain some insight into the molecular mechanisms of these photochemical and photophysical differences which are of great importance for the photolithographic application of these materials.

Mechanical Properties of Thin Films

The mechanical properties of thin films are different from those of bulk materials because of their unique microstructure, large surface-to-volume ratio, reduced dimensions, and the constraints caused by the substrate. Since the substrate is a key factor in the mechanical properties of single and multilayered thin film structures, this paper will limit itself to the mechanical properties of thin films on substrates. The mechanical prop­ erties of free-standing thin films were previously reviewed by Hardwick ( 1 ) . Because of the diversity of the subject and the sheer volume of pub­ lications, a complete review of the area of mechanical properties of thin films is impossible. Focus will be on thin metal and ceramic films with thickness less than I J-lm. Measurement techniques and recent results will be reviewed and areas of future work will be identified. Understanding the processes controlling the mechanical properties of thin film structures is important in a variety of scientific and technological applications. In the last few decade� the �cientific arena has seen the development of dry deposition processes, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), as well as the appearance of improved in situ characterization and analysis techniques: i.e. X-ray photoemission spectroscopy (XPS); Auger spectroscopy; low energy elec­ tron diffraction (LEED); and Brillouin scattering that allows relatively easy deposition of unusual microstructures, both crystalline and amorphous, as well as layered structures with controlled and reproducible periods of a few monolayers. Laminated thin film structures have been produced with tailored elastic and plastic properties. Detailed characterization and

Computer simulation of elastic and structural properties of thin films: I. (001) orientation in fcc metals

The structural and elastic properties of an unsupported thin metallic (001) film are investigated as function of the film thickness, Λ. The zero-temperature constant-stress relaxation procedure employed yields both the atomic structure and equilibrium dimensions as functions of Λ, for which a lattice-dynamics like calculation of the elastic constants is subsequently performed. Throughout, the results obtained by means of a Lennard-Jones (LJ) pair potential are compared with those obtained for a many-body potential of the embedded-atom-method (EAM) type. Although the detailed atomic relaxations differ substantially for the two potentials, the same generic elastic behavior as function of Λ is obtained. Quantitative differences are shown to arise from the rather different surface tensions obtained for the two potentials which, in turn, are due to the different shapes of the related cohesive-energy versus lattice-parameter curves for the perfect crystal. Remarkably, both potentials predict a strenghtening of certain elastic moduli and a softening of others. We conclude that the basic elastic properties of thin films are governed by the structural disorder associated with the very presence of the free surfaces and only indirectly by the dimensional changes.

Electronic and structural properties of thin films of Fe on Cu(1 1 1) and of the system Cu/Fe/Cu(1 1 1)

We have prepared thin films of Fe (0.5-5 monolayers) on Cu(1 1 1) and the sandwich system Cu(0.5-2 monolayers)/ Fe(1–5 monolayers)/Cu(1 1 1). Low-energy electron diffraction, Auger and angle-resolved photoelectron spectroscopy exhibited epitaxial growth of the films in the fcc structure at room temperature. Annealing leads to a rearrangement of the deposit in the form of three-dimensional Fe and Cu islands on top of the substrate. The Cu electronic states are not affected essentially by the Fe deposit. The Fe 3d states are characterized by a main peak at -∮.6 eV below the Fermi level, which we assign to the maximum density of states of the majority spin electrons.

Properties of Hg-based films and superlattices grown by molecular-beam epitaxy

We report the electrical, optical, and structural properties of thin films of HgTe, Hg1−xCdxTe, and Hg1−xMnxTe and superlattices of HgTe–CdTe and Hg1−xMnxTe–HgTe. All of these epitaxial films were deposited by molecular-beam epitaxy. The Hg1−xCdxTe films exhibit large electron Hall mobilities, specular reflectances, and sharp optical absorption edges. The Hg1−xMnxTe films, grown with x values of 0.03 and 0.10, also exhibit excellent optical and electrical properties. The p-type HgTe–CdTe superlattices exhibit large hole mobilities. Superlattices containing alternating layers of Hg1−xMnxTe and HgTe have also been successfully prepared. The Hg1−xMnxTe–HgTe multilayers are the first superlattices containing alternating layers of a Hg-based dilute magnetic semiconductor to be grown by any thin-film technique.

Automatic process control for artificially layered structures

There is an increasing interest in exploiting the properties of thin-film structures that are inherently complex and precise in the repetition and/or variation of their compositions. This is particularly true in the area of molecular-beam epitaxy. This technology is dependent on the control of evaporation sources to provide the precision necessary to fabricate these structures. At best, the Knudsen cell produces fluxes that have a nonlinear dependence on the controlling parameter, temperature, as well as an annoying dependence on the material level within the cell. At worst, the fluxes from electron beam evaporators are not only nonlinear but nonreproducible functions of their control parameter, power. A laboratory or small-system controller is described that combines a miniature ultrahigh vacuum (UHV) compatible, species selective deposition sensor with a software program that runs on a personal computer. It integrates composition control to 0.1 Å/s with the analog control of substrate temperatures, doping levels, and simpler functions such as shutters. This system has been running for 1 1/2 yr and has produced not only complex superlattice structures, but also novel nonlinear profiles such as parabolic composition grading in Ge–Si strained layer heterostructures in a reproducible, operator-independent mode.

The electrical and structural properties of thin films of polymers deposited from the vapour phase, with special reference to polypropylene

The electrical and structural properties of thin films of polymers deposited from the vapour phase, with special reference to polypropylene

Electrical optical and structural properties of thin films of In 2O 3:Sn deposited by hydrolysis

In this paper we present the results of studies on the electrical and optical properties and the structure of thin transparent conducting films of In 2O 3:Sn deposited on glass by the hydrolysis method in a quartz furnace with a rotating sprayer. With this new apparatus it is possible to obtain thin films of In 2O 3:Sn with better electrical and optical properties and of greater homogeneity; at the same time the reproducibility of the results is improved. The effect of spraying temperature on the properties of the In 2O 3:Sn films and their thickness was studied. With a rise in temperature (from 673 to 973 K) the thickness of the films increases together with the electrical conductivity but the optical transmission is somewhat reduced. It was found that a lower spraying temperature (673 K) the In 2O 3:Sn film is amorphous whereas at higher temperatures it crystallizes with a regular pattern, the lattice constants increasing linearly with temperature. Investigations of the effect of the volume of the sprayed substance on the sheet resistivity R □, thickness and optical transmission of two series of samples showed that In 2O 3:Sn films obtained from alcoholic solutions of In 2O 3 dissolved in HCl have better electrical properties than films obtained from alcoholic solutions of InCl 3 with a small admixture of HCl.

CuInS 2 films prepared by spray pyrolysis

The electrical, optical and structural properties of thin films of CuInS 2 prepared by spraying a solution of Cu 2Cl 2, InCl 3 and thiourea onto heated glass and alumina substrates are described. The polycrystalline films produced at prescribed spraying rates and substrate temperatures were nearly stoichiometric as shown by EDAX analysis, homogeneous, and had the sphalerite structure The films were p-type and their resistivity could be adjusted over the range 0.1 ω cm to very high values by controlling the temperature of the substrate during spraying. Heterojunction devices which exhibited a weak photovoltaic effect were prepared by combining these films with either single crystals of CdS or with sprayed films of CdS.

Structural properties of thin Bi 1− xSb x alloy films

Measurements of the structural properties of thin films of Bi 1−xSb x alloy using an electron microscope and X-ray diffractometer were performed. The change in the lattice parameter of the alloy depending on the Sb concentration was established to be in agreement with Vegard's law. The existence of texture in thin films of Bi 1− x Sb x alloy was also confirmed. The dependence of the linear dimension of the average size of the crystallites on the antimony concentration was investigated.

Investigation of electrophysical properties of thin film structures prepared by flash thermal evaporation from closed volume: A A Kastalskiy et al, Proc of All-Union Conf on Dielectric Electronics, FAN Tashkent 1973, 62 (in Russian)

Investigation of electrophysical properties of thin film structures prepared by flash thermal evaporation from closed volume: A A Kastalskiy et al, Proc of All-Union Conf on Dielectric Electronics, FAN Tashkent 1973, 62 (in Russian)

Some electrical properties of thin film copper–borosilicate glass–copper sandwiches intended for use as electron emitters

The electrical properties of thin film structures consisting of metal-insulator-meta sandwiches are investigated. Results for current-voltage characteristics, forming effects, temperature dependence of conductance, and the emission of electrons into n vacuum are described, particularly for the structure Cu-SiO/B2O3-Cu. Very high emission current densities are achieved for low applied voltages and with the cathode at or near room temperature. High values of hot electron attenuation length in both the copper electrode and in the insulator are obtained and the significance) of those high values is discussed.

1017. Optical and structural properties of thin films of amorphous antimony: I N Shklyarevskiy and A I Usoskin,Optika Spektroskop, 31 (4), 1971, 623–627 ( in Russian)

1017. Optical and structural properties of thin films of amorphous antimony: I N Shklyarevskiy and A I Usoskin,Optika Spektroskop, 31 (4), 1971, 623–627 ( in Russian)

Properties of thin films of zinc oxide prepared by a chemical spray method

The electrical, optical and structural properties of thin films of zinc oxide in the thickness range 10–400 nm on glass and fuzed quartz substrates have been investigated. The films were prepared using a new chemical spray technique which permitted deposition on either insulating or conducting substrates with a high degree of control over both the dimensions of the coatings and their electrical properties. The effects of variations in film thickness and heat treatment in oxygen have been examined and an assessment has been made of the dimensions of the depletion layer and of the diffusion coefficient of interstitial zinc in zinc oxide. Films with thicknesses greater than 40 nm are stable for long periods and show a crystalline structure with a preferred orientation of the c-axis normal to the substrate. An amorphous phase together with crystallites is apparent in films less than 40 nm thick. However, these films are unstable and show crystallite growth after storage at room temperature. In general, the optical properties of the films correspond with those of films prepared by other methods.

Structural Investigation of Thin Films

In the investigation of the structural properties of thin films by x-ray diffraction the lack of material, interference from the substrate, and generally, high orientations of the grains makes analysis of the films very difficult. In order to fully characterize a thin film for stresses (macro- and micro-), grain size, orientation, faulting probability, and solid solution effects, it is necessary to employ a range of x-ray techniques with some special experimental conditions. It is shown that a full strnctural analysis of thin films (alloy films included) can be routinely carried out making comparison of different types of thin film possible. Two 12-kÅ-thick Al films are characterized and it is shown that large errors can occur in residual stress and solid solution effect if the data is not handled properly.

The Relation of Thin Films to Corrosion★

Abstract Recent studies of thin oxide films isolated from stainless steels and other ferrous alloys have provided new information on surface properties. Correlations between the unique compositional and structural properties of thin films and alloy corrosion behavior in various corrosive environments have been established. Evaluation of the resistance to pitting corrosion of silicon-modified Type 316L stainless steel is described as a typical example of an application of a film study to corrosion research. In this case, improved corrosion behavior was correlated with a mutual film-enrichment of silicon and molybdenum and a film-depletion of iron. Experimental alloys of improved purity were prepared and evaluated. Effects of alloy purity, carbon content, and alloying additions were found to influence strongly surface behavior and corrosion resistance. The mechanism of resistance to pitting corrosion and the protective nature of the associated oxide films are interpreted in terms of the chemistry of hydrated heteropoly acids containing oxides of silicon and molybdenum. 3.8.4