Crystallization of hydrogenated amorphous silicon thick films deposited by dc glow discharge on molybdenum substrates was studied by Raman scattering and x-ray diffraction. Investigation was made as a function of amorphous silicon film deposition temperature. On heating the films at a rate of 5 °C/min to 650 °C for various times, it was observed that the film deposited at 300 °C started crystallization faster than the film deposited at 150 °C. The degree of cirystallinity increased with increasing annealing time for all the films. However, at all annealing times, the degree of crystallinity for the annealed film deposited at 150 °C was higher than that of the annealed film deposited at 300 °C, indicating that the crystallization growth rate was higher for the film deposited at a lower temperature. These results were consistent with the dark conductivity measurements. The film deposited at 150 °C showed a photoresponse which increased with increasing annealing time whereas no photoresponse was observed for the film deposited at 300 °C. This was probably due to the degree of crystallinity and grain size being much larger for the film deposited at 150 °C than the film deposited at 300 °C.

Laser crystallized amorphous silicon thin films on quartz exhibit a peak in the grain size, electron mobility and the Si (111) x-ray intensity as a function of the laser fluence, substrate temperature, film thickness, and the number of laser shots per unit area. The peak in grain size has also been shown to be dependent: on the stability of the pulse-to-pulse laser energy density, particularly at high shot densities. The shape of the distribution profile of the pulse-to-pulse laser fluence can significantly alter the grain growth at higher shot densities. The modified growth can be expressed by a simple model based on the mean and standard deviation of the laser energy density relative to the characteristic fluence at which the grain size, mobility, and Si (111) x-ray intensities are maximized.

Excimer laser crystallized Si thin films on fused silica substrates exhibit a peak in the average grain size as a function of laser energy density. The average grain size increases with increasing laser fluence until a maximum value , approximately 10 microns for a 100 nm thick Si film, is achieved. The peak in grain size is accompanied by a peak in the electron Hall mobility. Further increases in the laser fluence result in a decrease in the Si grain size and an increase in the intragranular defects. A small energy range of 40 mJ/cm2 exists in which this peak in grain size can be achieved. Cross section TEM has shown that when the peak laser fluence is exceeded, the fused silica substrate can be as rough as 17 nm. Atomic force microscopy. performed on the substrate surface after the Si has been etched off, also shows that the magnitude and spatial frequency of the roughness increases when the critical laser fluence is exceeded. This degradation of the interface may also produce sites for stacking faults to form during the solidification of the Si. This result and results of simulations of the temperature of the interface during crystallization suggests that the peak energy range exists after the complete melting of the Si thin film and before the silica substrate starts to soften.

The electrical resistivity and microstructure of sputtered germanium film were characterized as a function of anneal temperature from 400 to 700°C. The as-deposited sputtered Ge film had an amorphous structure with resistivity of 165 Ω-cm which was maintained after annealing up to 540°C. After annealing above 550°C, the resistivity dropped by almost four orders of magnitude to ∼0.027 Ω-cm. The sharp transition of resistivity at 550°C is believed to be due to the recrystallization of Ge film from the as-deposited amorphous structure. The ohmic contact property on Ge films was also evaluated using sputtered tungsten. Low resistance ohmic contacts were obtained both on as-deposited and annealed Ge films, with typical ohmic contact resistance of 0.05 ± 0.008 Ω-mm on annealed Ge films. The W contacts were thermally stable after annealing up to 650°C.

The morphology and texture of polycrystalline LPCVD GexSi1-x alloys have been studied for various deposition temperatures and for x = 0, x = 1 and x ≈ 0.3. The transition temperature of amorphous to polycrystalline growth is much lower for Ge and GexSi1-x than for Si. Just above this transition temperature, we observed a (220) orientation for all polycrystaline layers grown. At elevated temperatures a change to the (004) orientation for poly-GexSi1-x and (331) for poly-Si and poly-Ge is noted.

The energies and atomic structures of tilt and twist boundaries in Si have been examined by using the tight-binding electronic theory, and the reason why twist boundaries are seldom found in polycrystalline Si has been investigated. About the frequently observed {122} Σ=9 and {255} Σ=27 tilt boundaries, the configurations without any coordination defects consistent with the electron microscopy observations have relatively small interfacial energies with small bond distortions. About the <111> Σ=7, <011> Σ=3 and <001> Σ = 5 twist boundaries, the configurations contain larger bond distortions or more coordination defects, and much larger interfacial energies than those of the tilt boundaries. The <001> twist boundaries have very complex structures as compared with the other twist boundaries, which can be explained by the morphology of the ideal surfaces. The stability of the tilt boundaries in Si can be explained by the viewpoint of the stable structural units consisting of atomic rings.

The electrical and piezoresistive properties of in-situ doped PECVD silicon films deposited on oxided silicon wafers have been investigated. One series of films was deposited in the so-called microcrystalline state at 450°C. The other set of samples was deposited in the amorphous state at 320°C and subjected to rapid thermal annealing. Structural properties (grain size, texture, residual stress) were evaluated experimentally through TEM and grazing angle X ray diffraction and related to the measured gauge factor. A maximum longitudinal gauge factor of 28 is measured in the case of advantageously textured microcrystalline material, the magnitude of the gauge factor decreasing sharply for randomly oriented material. For the amorphous deposited and subsequently annealed material, the longitudinal gauge factor is in the range 22–27 depending on dopant concentration. These experimental features are compared to the results of a theoretical approach of piezoresistance in polysilicon. We derive various expressions of the gauge factor according to the assumptions of either constant stress or constant strain within the aggregate. In the case of untextured films, analytical Voigt-Reuss-Hill averages for the elements of piezoresistive and elastoresistive tensors lead to greatly simplified expressions. Theoretical estimates are shown to be in reasonable agreement with the experimental measurements. This confirms the great potential of PECVD microcrystalline and polycrystalline silicon for strain gauges.

A gas mixture consisting of TiCl4, H2 and N2 was fed into an externally-heated steel tube, and TiN was deposited on the inner wall by CVD. Microstuctures of the films were observed and their relationships with the preferred crystal orientations were studied. Distributions of the film growth rate and gas concentrations along the axial direction were calculated.

By comparing the film microstructures with the calculated local deposition conditions, it is shown that formation of the films with (110) preferred orientation correlated with the conditions at high temperature and low partial pressure of TiCl4 on the substrate.

The structure, morphology, and electrical properties of pulsed laser deposited NbNx (0 ≤ x ≤ 1.4) thin films have been investigated. Films were deposited from Nb metal targets on oriented MgO (100) and amorphous fused silica substrates as a function of substrate temperature and ambient pressure. A reducing atmosphere (N2 with 10% H2) was used to prevent oxide formation. At elevated temperatures, the N/Nb ratios of films deposited on MgO, as determined from Rutherford Backscattering Spectroscopy, increased from 0 −1.4 as the ambient pressure was varied from vacuum to 200 mTorr, respectively. NbNx films (x=l) were deposited at 600 °C and 60 mTorr. Both the structure and electrical properties of the deposited films varied strongly with the substrate type. On fused silica, NbN films were poorly crystalline with low critical temperatures (Tc ∼ 8 – 11 K) and low critical currents (Jc (4.2 K) ∼ 2 MA/cm2), whereas on MgO the NbN films were oriented and had better transport properties (Tc ∼ 16.4 K and Jc (4.2 K) = 7.1 MA/cm2).

Reactively-sputtered, polycrystalline thin film aluminum nitride (AlN) is an attractive material for use in acoustic wave devices, for which it requires a strong preferred orientation, similar to that found in epitaxial films. This investigation evaluated the grain structure including preferred orientation, grain size, and surface morphology of sputtered A1N films. The characterization techniques utilized included x-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The results revealed two types of grain structure: 1) a single-grain columnar structure that is perfectly oriented in the [001] direction throughout the entire film thickness and 2) a multiple-grain columnar structure that possesses a strong [001] orientation at the bottom of the film and a tilted [001] combined with other orientations at the top of the film. Strong correlations between orientation and surface morphology, oxygen content, and grain size were observed, namely higher degrees of c-axis orientation correlated with lower mean surface roughness values, reduced oxygen concentration, and narrower grains.

Zirconium nitride films on silicon substrates have been prepared by DC magnetron enhanced reactive sputtering in a N2/Ar gas mixture under various experimental conditions. The films properties (chemical composition, structure, morphology and optical response) were investigated and related to the experimental conditions. It is shown that these properties are strongly related to the target current density which governs the deposition rate, to the deposit thickness, to the nitrogen partial pressure and to the residual gas contamination. The objective of this paper is to detect the minimum film thickness threshold under which a zirconium nitride coating cannot be used in decorative applications.