Papers by Keyword: Hall

Abstract: Loudness is one of the three basic parameters to assess the auditorium sound quality with reverberation time and balance together, it will be discussed in this paper. There are three expressions evaluating the loudness: listening level, the strength index and the mean forte sound pressure level of tutti-sound (LpF). Each of them has their merits and shortcomings. This paper will focus on these three expressions and the feasibility of checking and accepting acoustics of the hall by loudness.

Abstract: P-type microcrystalline silicon films prepared by electron cyclotron resonance（ECR）PECVD are studied here. Silane diluted with Ar (SiH4/Ar=1/19) is used as a source gas and diborane (B2H6) diluted with H2 (100ppm) as doping gases. The effect of flow rate of doping gas on the microstructures and electrical properties of the films were investigated. Raman spectroscopy and X-ray diffraction were used to determine the film structure; AFM was employed to characterize the film surface topography; Hall measurements were carried out on the doped films to determine the carrier type, carrier concentration, and Hall mobility. The optical quality was measure by transmission spectrum.

Abstract: Silicon carbide as a material for electronic devices still has substantial problems concerning its structural quality and defects. It has been shown that dopants can have a big influence on structural properties like polytype stability and dislocation statistics [1]. We will discuss the effect of an isoelectronic dopant in silicon carbide. Germanium, being a member of the 4th group in the periodic table of elements like silicon and carbon, will not influence the electrical properties of the material such as e.g. aluminum. In our experiments we reached concentrations of up to 1*1020 cm-3. We have observed an impact on the polytype stability during sublimation growth with in-situ germanium incorporation. We investigated an influence on the dislocation statistics during growth and, hence, varying germanium concentration. We found only a slight decrease in mobility during Hall measurements but no severe changes in electrical properties of the material.

Abstract: D-band electron paramagnetic resonance (EPR) measurements as well as X and Q-band field-swept Electron Spin Echo (ESE) and pulsed Electron Nuclear Double Resonance (ENDOR) studies were performed on a series of n-type 4H-SiC wafers grown by different techniques including sublimation sandwich method (SSM), physical vapor transport (PVT) and modified Lely method. Depending on the C/Si ratio and the growth temperature the n-type 4H-SiC wafers revealed, besides a triplet due to nitrogen residing on the cubic site (Nc), two nitrogen (N) related EPR spectra with g||=2.0055, g⊥=2.0010 and g||=2.0063, g⊥=2.0005 with different intensities. In the samples with low C/Si ratio the EPR spectrum with g|| =2.0055, g⊥=2.0010 consists of a triplet with low intensity which is tentatively explained as a N-related complex, while in the samples with high C/Si ratio the triplet is transformed into one structureless line of high intensity, which is explained as being due to an exchange interaction between N donors. In the samples grown at low temperature with enhanced carbon concentration the EPR line with g||=2.0063, g⊥=2.0005 and a small hyperfine (hf) interaction dominates the EPR spectrum. It is attributed to N on the hexagonal lattice site. The interpretation of the EPR data is supported by activation energies and donor concentrations obtained from Hall effect measurements for three donor levels in this series of 4H-SiC samples.