ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sun, 09 May 2021 23:06:16 GMT2021-05-09T23:06:16Z50111- Variation of trapping/detrapping properties as a function of the insulator sizehttps://scholarbank.nus.edu.sg/handle/10635/98548Title: Variation of trapping/detrapping properties as a function of the insulator size
Authors: Oh, K.H.; Ong, C.K.; Tan, B.T.G.; Gressus, C.L.; Blaise, G.
Abstract: Using the scanning electron microscope we have investigated the physical parameters determining the size effect of various dielectric samples submitted to a surface electric field. It is shown that the size effect is a function of the static permittivity and of the space charge distribution. The results are explained by the consideration of charge diffusion and polarization relaxation processes resulting from the space charge formation. A one-dimensional mathematical model has also been used to describe space charge distribution. The findings were consistent with the experimental observations.
Fri, 01 Jan 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/985481993-01-01T00:00:00Z
- Variation of the relative permittivity of charged dielectricshttps://scholarbank.nus.edu.sg/handle/10635/53254Title: Variation of the relative permittivity of charged dielectrics
Authors: Ong, C.K.; Song, Z.G.; Oh, K.H.; Gong, H.; Le Gressus, C.
Abstract: The variation of the relative permittivity of charged dielectrics with trapped charge density has been investigated by a time-resolved current method, in conjunction with a mirror image method employing a scanning electron microscope. The calculation is made by a mathematical expression derived from classical electromagnetic theory. It is found that the relative permittivity of the charged area in the polymethylmethacrylate sample increases with the trapped charge density and saturates at a certain value of the trapped charge density. These observations have been discussed by analogy with the dielectric saturation occurring at a high applied external electric field. © 1998 American Institute of Physics.
Thu, 01 Jan 1998 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/532541998-01-01T00:00:00Z
- Charge trapping on different cuts of a single-crystalline α-SiO 2https://scholarbank.nus.edu.sg/handle/10635/95977Title: Charge trapping on different cuts of a single-crystalline α-SiO 2
Authors: Gong, H.; Le Gressus, C.; Oh, K.H.; Ding, X.Z.; Ong, C.K.; Tan, B.T.G.
Abstract: A scanning electron microscope is employed for the investigation of charging on different cuts of an α-SiO2. A method for the determination of trapped charges is proposed. Charging on different cuts is observed to decrease in the order of z cut, 30° cut, 45° cut, and 60° cut of the α-SiO2. This phenomenon is related to permittivity, defect density, and stress of the samples. Details of the experiments and the method of charge determination are given.
Fri, 01 Jan 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/959771993-01-01T00:00:00Z
- Dielectric polarization relaxation measurement in α-SiO2 by means of a scanning electron microscope techniquehttps://scholarbank.nus.edu.sg/handle/10635/96217Title: Dielectric polarization relaxation measurement in α-SiO2 by means of a scanning electron microscope technique
Authors: Oh, K.H.; Le Gressus, C.; Gong, H.; Ong, C.K.; Tan, B.T.G.; Ding, X.Z.
Abstract: A scanning electron microscope is used as a tool to study dielectric relaxation processes in α-SiO2 by measuring the leakage current in the sample surrounded by a metallic aperture. A transient time (t t) of the order of a few seconds appears before the steady-state current is established. The time dependence of the trapping rate is found to follow a power law and to be related to relaxation processes of a dielectric under electrical and thermal stress.
Fri, 01 Jan 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/962171993-01-01T00:00:00Z
- Simple microwave method of moisture content determination in soil sampleshttps://scholarbank.nus.edu.sg/handle/10635/97926Title: Simple microwave method of moisture content determination in soil samples
Authors: Oh, K.H.; Ong, C.K.; Tan, B.T.G.
Abstract: A simple empirical equation for the measurement of the moisture content in a soil sample by using a microwave bridge to measure attenuation and phase shift through the sample is proposed. A calibration chart has been obtained from this equation for the convenient determination of the moisture content in a soil sample of unknown density. The validity and applicability of the equation has been confirmed by measurements on several soil samples of varying densities and thicknesses.
Sat, 01 Oct 1988 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/979261988-10-01T00:00:00Z
- A Monte Carlo model for trapped charge distribution in electron-irradiated α-quartzhttps://scholarbank.nus.edu.sg/handle/10635/95641Title: A Monte Carlo model for trapped charge distribution in electron-irradiated α-quartz
Authors: Oh, K.H.; Ong, C.K.; Tan, B.T.G.; Le Gressus, G.
Abstract: The space dependence of charge carriers trapped in α-quartz under electron-beam bombardment is investigated using a Monte Carlo algorithm. The average energy of the electron after being detrapped from a trap site is first calculated by considering both the polar and nonpolar phonon scatterings. Later, the detrapping and trapping rates are also included in the model to obtain a stable trapped charge distribution, which is found to be dependent on the size as well as the temperature of the sample. Comparisons with experimental results of the size effect on the dielectric strength obtained from a scanning electron microscope are also made.
Fri, 01 Jan 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/956411993-01-01T00:00:00Z
- Monte Carlo simulation of size effect on the dielectric strength of α-quartzhttps://scholarbank.nus.edu.sg/handle/10635/98802Title: Monte Carlo simulation of size effect on the dielectric strength of α-quartz
Authors: Oh, K.H.; Kong, C.K.; Tan, B.T.G.; Gressus, C.Le.
Abstract: The size effect(SF) in a dielectric submitted to a surface space charge field was defined as the slope of the curve ln(Vs/r) vs ln(r), Vs and r are the critical surface potential and length of the sample respectively by Oh et al[1]. SF is an important material parameter affecting breakdown voltage, space charge detrapping field, friction coefficient, wear and fracture toughness of the dielectric. The findings of SF have many potential important application in electrical and mechanical engineering. In this report, we investigate this problem experimentally and theoretically, the experimental was carried out in the SEM using the electron beam to bombard the dielectric. The space charge distributions for different sizes are obtained separately from macroscopic equations and microscopic simulation.
Fri, 01 Jan 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/988021993-01-01T00:00:00Z
- ELIMINATION OF AMBIGUITY IN MEASUREMENT OF PERMITTIVITY WITH SHORT-CIRCUITED WAVEGUIDE.https://scholarbank.nus.edu.sg/handle/10635/96441Title: ELIMINATION OF AMBIGUITY IN MEASUREMENT OF PERMITTIVITY WITH SHORT-CIRCUITED WAVEGUIDE.
Authors: Oh, K.H.; Ong, C.K.; Tan, B.T.G.
Abstract: A new experimental parameter is introduced to eliminate the ambiguity in the short-circuited waveguide method for measuring permittivity. The results of our measurements using this technique for some standard materials are also presented.
Thu, 01 Jan 1987 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/964411987-01-01T00:00:00Z
- Investigation of charging on α-quartz facets by a SEM techniquehttps://scholarbank.nus.edu.sg/handle/10635/98767Title: Investigation of charging on α-quartz facets by a SEM technique
Authors: Gong, H.; Le Gressus, C.; Oh, K.H.; Ding, X.Z.; Ong, C.K.; Tan, B.T.G.
Abstract: From a SEM mirror image for the charge potential, electrons trapped on different cuts of an α-quartz are determined. Different charging abilities for the various cuts are observed, and this phenomenon is related to permittivity, defect density and stress of the samples.
Fri, 01 Jan 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/987671993-01-01T00:00:00Z
- Field dependence of the overshoot phenomena in InPhttps://scholarbank.nus.edu.sg/handle/10635/96628Title: Field dependence of the overshoot phenomena in InP
Authors: Oh, K.H.; Ong, C.K.; Tan, B.T.G.
Abstract: The Ensemble Monte Carlo method has been used to investigate the velocity overshoot effect in InP, for applied fields greater than 10 kV cm-1. We confirmed that the effect that occurs in InP is caused by the rapid transfer of charge carriers from a high mobility Γ-valley to a low mobility L-valley. Detailed comparison with the results obtained for GaAs by Xing Zhen [Ensemble Monte Carlo modeling of high-field transport and ultra-fast phenomena in compound semiconductors, Thesis (1990)] has also been made and commented on. © 1992.
Wed, 01 Apr 1992 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/966281992-04-01T00:00:00Z
- Thermal control unit for microwave measurements of conductivity of a semiconducting materialhttps://scholarbank.nus.edu.sg/handle/10635/98353Title: Thermal control unit for microwave measurements of conductivity of a semiconducting material
Authors: Oh, K.H.; Ong, C.K.; Tan, B.T.G.
Abstract: A simple thermal control unit, together with a transmission microwave bridge have been constructed for the measurement of electrical conductivity at the X-band frequency of a silicon sample in the range 323 to 573 K. The temperature dependence of the conductivity and hence the band gap of Si were obtained. The technique may be used for other semiconducting materials.
Sun, 01 Oct 1989 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/983531989-10-01T00:00:00Z