The existence of both strain and disorder at the interface of thermally grown Si02 or plasma-deposited Si3N4 films on vicinal Si(111) was ascertained unambiguously by frequency, polarization, and crystal orientation dependent studies of optical second-harmonic generation. The strain was seen to cause a redshift of 40 and 70 meV of the interband critical points Fo and FI compared with the bulk silicon values. The disorder is observed by the perturbation of states out of the silicon bulk bands into the gap. Both at terraces and at steps, the density of these charge traps is found to be considerably reduced after rapid thermal annealing. PACS numbers: 73.20.r, 42.65.Ky, 68.35.Bs Strain and order or disorder at the heterointerfaces in semiconductors significantly affect the electrical device characteristics [1 -4]. For instance, the disorder of

We report the first investigation of the optical anisotropy of H- and SiO2-terminated Si surfaces. We examine six different orientations: (110); several vicinal (111); (113); and vicinal (001). Observed reflectance-difference (RD) spectra fall into two classes according to whether the surface normal is oriented from [111] toward [110] or [001], being consistent with the existence of different step configurations for the two cases. In the (110) class the spectral lineshapes resemble the imaginary part of the Si dielectric function, while in the (001) class they are similar to the energy derivative of the Si reflectance spectrum. To make surface and interface comparison meaningful, we develop an analytic method for correcting interface spectra for the relatively large effects of overlayer thickness. Thickness-corrected RD spectra of Si–SiO2 interfaces are found to differ in small but distinct ways from those of H-terminated surfaces of the same orientation, specifically in the enhancement of spectral features and the appearance of an optical absorption band near 3 eV. Rapid thermal annealing between 900 and 1000 °C increases oxidation-induced interface absorption for the (113) surface and red-shifts the entire spectrum for the (110) surface. We attribute these effects to a relatively high degree of order for (110)-class steps and lower order for (001)-class steps.

Articles you may be interested inInherent interface defects in thermal (211) Si / SiO 2 : 29 Si hyperfine interaction AIP Conf.This paper reports on a study of the intrinsic stress and strain in thin films ofSi0 2 prepared by the thermal oxidation of crystalline silicon. We focus on the relationship between the inhomogeneity of thin-film properties and the thermal history of the oxide film, including both film growth and thermal annealing. We show that this film can be inhomogeneous in the sense that oxide formed initially at the silicon-silicon dioxide (Si/Si0 2 ) interface has been annealed at the growth temperature for the time required for film growth, whereas newly formed oxide at the growth interface has not been annealed for any appreciable period. We demonstrate that thermal annealing cannot completely remove the thickness dependence in the strain induced by the mismatch between the molar volumes of silicon and silicon dioxide at the growth interface, subject to constraints introduced by the chemical bonding structure at that interface. Based on laser-beam deflection and photoreflectance measurements, we show that there is always a substantial residual intrinsic interfacial stress, and that is independent of the growth temperature, and thermal annealing. A time scale for describing thermal relaxation of stress and strain profiles is given by the ratio of process time to the viscoelastic relaxation time at the processing temperatures.

Correlations between midgap interface state density (Dit) and thickness-averaged stress in thermally grown SiO2 thin films have been investigated by infrared spectroscopy, an optical beam deflection technique, and capacitance-voltage measurements. We find no correlations between Dit and either (i) the maximum stress in the Si or SiO2 at the Si/SiO2 interface or (ii) the stress gradient in the SiO2 film. By direct measurements of the strain-induced bending of the Si wafer, and by calculating the microscopic strain from the SiOSi bond-stretching vibrational frequency, we have established linear relationships between Dit and the thickness-averaged stress and strain in the oxide.

To investigate the characteristics of electron oscillations generated under simplified conditions, an experimental plane-electrode triode has been constructed. Its plane emitting surface is 25 mm. in diameter. The cathode-plate distance can be continuously varied while the valve is in operation. External circuits may be connected to the electrode leads in such a way that the resultant oscillating circuit is effectively continuous from the electrodes to the terminating condenser. With no external circuit connected to the valve, oscillations are maintained whose wave-length varies with grid voltage exactly according to the Barkhausen equation A2V= constant. Their mechanism appears to be confined to the grid-cathode space. They are produced only when the grid current IS space-charge-limited. When an external circuit is used, oscillations are maintained at very low emissions. Their wave-length is always identical with some resonant wavelength of the circuit. Their mechanism may be confined to the grid-plate space, or may extend over the cathode-plate distance. First and second-order dwarf waves are observed. I t is shown that much more complex experimental results can be analysed on the basis of the conclusions drawn from the simplified experiments. A brief discussion of the applicability of existing theories to the simplified experiments is given.