Kun-Wei Lin

Enhanced Cu‐Teflon adhesion by presputtering prior to the Cu deposition

Adhesion of Cu to Teflon has been studied by depositing Cu to Teflon with and without a presputtering prior to the Cu deposition. Without presputtering, a weak adhesion is observed, with a value of 1 g/mm, which fails the scotch tape test. With a presputtering using 500 eV Ar+ ions, the adhesion rapidly increases, becoming evident after a sputtering of 10 s, and reaches maximal increases of 50 times at longer sputtering times. All the Cu films deposited after presputtering show strong adhesion, and can only be removed by forceful scratching with sharp tools. The presputtering was shown to change both the surface morphology of Teflon, with the deposited Cu following the morphologies created, and the interface chemical bonding between Cu and Teflon as revealed by x‐ray photoelectron spectroscopy. Exposure of the presputtered Teflon to air prior to the Cu deposition shows no effect on the strong adhesion obtained. An interface bonding model is suggested for the enhanced adhesion observed.

LOW-TEMPERATURE LUMINESCENT PROPERTIES OF DEGENERATE P-TYPE GAAS GROWN BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION

Low‐temperature (20 K) luminescent properties of heavily carbon‐ and zinc‐doped GaAs grown by low‐pressure metalorganic chemical vapor deposition were investigated. The luminescence linewidth became broader at low temperatures when p≳4×1019 cm−3 due to the appearance of a shoulder peak. The main peak shifted to low energy when the dopant concentration was increased; however, the shoulder peak was at around 1.485 eV and was nearly independent of the dopant concentration. The peak of the band‐to‐acceptor transition occurred at low temperature and dominated the emission spectra of degenerate GaAs. The peak energy of Zn‐doped samples was lower than that of C‐doped samples because of the existence of defects. The excitation power intensity was varied to investigate the behavior of the shoulder peak for both types of dopants. The shoulder peak was a part of the main peak because of the recombination between the conduction band and the bottom of the impurity band.

ANALYSIS OF CAPACITANCE-VOLTAGE CHARACTERISTICS FOR TWO-DIMENSIONAL MULTI-CONDUCTOR IN LIQUID CRYSTAL DISPLAYS

The capacitance voltage characteristics for the two‐dimensional multi‐conductor in liquid crystal displays (LCDs) are numerically derived by the method of successive over relaxation (SOR). The nonlinear and anisotropic properties of dielectric constant in the LC cell depend on the orientation of LC molecules under the influence of inhomogeneous electric field. An LC continuum theory implemented by tensor takes elastic anisotropy and inhomogeneous electric field into consideration to calculate the two‐dimensional molecule orientations and potential distribution in LCDs. The dependence of capacitance on applied voltages and the geometric of LC cell is quantitatively described. Nonlinear capacitance results in capacitive coupling which causes flicker and adversely degrades image retention in LCD.

Anomalous mobility enhancement in heavily carbon‐doped GaAs

An anomalous mobility enhancement and metallic‐type conductivity were observed in heavily carbon‐doped GaAs grown by low‐pressure metalorganic chemical vapor deposition. The 77 K mobility was slightly lower than that of 300 K for hole concentration between 1×1018 and 4×1018 cm−3. However, the 77 K mobility was enhanced from p≳4×1018 cm−3, and the 300 K mobility slowly decreased with increasing hole concentration that ranged from 7×1018 to 3×1019 cm−3. As a result, the 77 K mobility was around 50%–60% greater than the 300 K mobility due to the metallic‐type conductivity.

Doping of InGaP epitaxial layers grown by low pressure metal-organic chemical vapor deposition

Abstract DEZn and H 2 Se were utilized as p- and n-type dopant sources for the growth in InGaP layers by low pressure metal-organic chemical vapor deposition (LP-MOCVD). The decrease in intensity of the extra spots of electron diffraction indicates that disordering is induced by the zinc doping. Streaky and wavy diffraction patterns demonstrate the formation of anti-phase domains caused by the Se dopant incorporation. The growth rate of the grown layer is reduced by more than 10% owing to the dopant incorporation. A photoluminescence emission energy difference of 141 meV between undoped and Zn-doped (5.8 × 10 18 cm −3 ) InGaP was obtained. The effects of doping on disordering, degeneracy of quasi-Fermi level and lattice constant reduction of grown layers were included in this study.

Analysis of the operation of mixed-mode twisted nematic cells

Abstract Analysis of mixed-mode twisted nematic (MTN) cells in one-and two-dimension simulation are presented. Two-dimensional simulation reveals that the light leakage in the region of the reverse tilt domain in MTN cells reduces the contrast ratio with a novel method by adding a bias voltage onto Silicon substrates, the light leakage can be suppressed and the open ratio of the cell is greatly improved.

ANALYSES OF THE OPERATION OF IN-PLANE SWITCHING DISPLAY MODE OF LIQUID CRYSTAL DISPLAY

The IPS mode of LCD h i i s wide viewing angle compared with TN mode, but requires it higher driving voltage to reach a maximum transmittance. The electro-optical properties of IPS mode :ire compliciited and can not be fully revealed by an analytic form. In this letter, the electro-optical properties of in-pliinc switching mode were analyzed by LC continuum theory to achieve ii maximum transmittance at a low opcriiting volt;ige. Although the in-plane switcliing (IPS) mode of LC has been investigated as early as two decades ago[ 11121. until recently wide viewing angle of this display is rediscovered and demonstrated [3]I4115]. Unlike tlie well-known twisted nematic (TN) cells. the liquid crystal molecules of tlie IPS mode keep tlicir dircctors parallel to tlie plane of substrates and ;in inter-digital electrode is used to switch the molecule dircctors to be in-plane oriented to control the transniittance. The optical effect of tlie IPS mode is suggested to fiinclion as ii wave-plate where tlie maximum transmittancc can occur. Tlie esact operation of IPS mode is very complicated and not well understood. In this paper. n e have analyzed the electrooptical properties and tlie operations of IPS iiiode to achieve an optimal perroniiance at a low operating voltage. Tlie electrode of IPS cell is quite different froni normal TN cell, which is parallcl to tlic glass substrate. The schematic configuration or IPS inode cell is shown in Fig. 1. Tlie inter-digital electrodes itre parallel to y-asis, while the direction LC niolccitlar ;tiid polarim are set at an angle /? to x-axis. When no voltagc is applied to interdigital electrodes, incident light is blocked by tlie two cross polarizers. When a voltage is turn on between tliem. LC directors are forced to align \ \ i t 1 1 the electric field escepl tlie LC layer adjacent to tlie boundary. due to strong anchoring. The deforniation of the LC iiiediuiii results i n rctardatioii, hence. causing light to leak through two crossed polarizers. The deformtion distribution of LC directors are quite complicated aiid can not be revealed by analytic forins. In order to evaluate the electro-optical propertics of IPS, an LC continuum theory of elastic anisotropy and inhomogeneous electric field are used to calculate the LC director profiles 161 and estended Jones matrix methods [ 71 to conipiite the optical transmittancc. 2 Analyzer Polarizer f Fig. 1 Configuration if In-Plane Switching. Accordiiig to the iiietliods mentioned above, we have calculatcd the electro-optical properties of IPS mode by using tlie paranictcrs i n Table 1. Calculated director distribution. electric ficld, and optical transinittance. are sliowm in Figs. 2(a). (b) and (c), respectively. with respect to the electrode position. As tlie driving voltage increases, tlic transmittancc of the area between Vconi and Vpixel clcctrodc incrcascs. ,as shown i n Fig. 2(c). Therc csists a broad iiiaxiniuiii traiisniittance in tlic iiiiddle area

Reactive Ion Etch of GaAs and AIGaAs Using BCl 3 , SiCl 4 and SF 6 .Instead of CCl 2 F 2

In the past, CCl 2 F 2 had been widely used in the dry etching process of the GaAs-based materials, However, it causes ozone depletion and is detrimental to the environment. In order to prevent further ozone depletion, it is necessary to search for some substitutedl gases. In this study, chloric gases, like BCl 3 and SiCl 4 , were used to provide an alternative way for the reactive ion etch of GaAs and AlGaAs. To provide high etching selectivity between GaAs and AlGaAs, a fluorine containing gas SF 6 is added, to increase the etch rate of GaAs than that of AlGaAs, which is due to the formation of non-volatile solid AlF 3 . In this study the etching characteristics of the BCl 3 /SF 6 , SiCl 4 /SF 6 were studied and high etching selectivity between AlGaAs/GaAs is achieved.

Semi-insulating iron-doped indium phosphide grown by low-pressure metal-organic chemical vapour deposition

Abstract(C5H5)2Fe and Fe(CO)5 were used as the 3d transition-metal dopant sources in the growth of semi-insulating InP epitaxial layers by low-pressure metal-organic chemical vapour deposition (MOCVD). From the bright- and dark-field images of transmission electron microscopy (TEM) analysis, many precipitates were observed. Three extra peaks in the X-ray diffraction pattern were found. The peaks of band-band recombination, donor-acceptor pair recombination transitions and the recombination of donor-acceptor pair with one-phonon emission were observed in the short-wavelength range of low-temperature photoluminescence measurement. Three Fe-related peaks were observed at 0.7079, 0.6897 and 0.6683 Ev. For a wide range (10–600) of In/Fe molar fraction, the resistivity remained at high values (about 108 Ω cm) and the highest resistivity appeared at 5 × 108 Ω cm for a 1 Μm layer with a breakdown voltage of 9 V.