摘要:

The effect of surface nucleation on the evolution of crystalline microstructure during the solid phase crystallization (SPC) of an amorphous Si (a-Si) film, deposited by low pressure chemical vapor deposition (LPCVD) onSiO2,has been investigated. The surface nucleation phenomenon was observed by suppressing the interface(a-Si/SiO2)nucleation by the incorporation of oxygen atoms during the initial deposition period ofa-Si. It was found that the surface-nucleated polycrystalline Si (poly-Si) had equiaxial grains with the size of about 3–5 &mgr;m, while interface-nucleated one had elliptical grains with the size of about 0.3–1 &mgr;m. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119437

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A theory is developed which explains how sample rocking during ion beam sputtering erosion can inhibit ripple formation, observed with monodirectional ion incidence, on radiation amorphisable materials. The model assumes curvature dependent sputtering yield and random ion arrival and sputtering as roughening processes and radiation mediated viscous flow and ballistically driven effective surface diffusion as smoothing processes. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119438

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Crystallographic orientations between thin-sputtered Cu film and &bgr;-Ta adhesion layer have been studied using high resolution electron microscopy and electron diffraction. Tetragonal &bgr;-Ta deposited onSiO2has a strong texture with its closest packed plane (002) parallel to the film surface. On (002) &bgr;-Ta, the growth of (111) Cu is preferred. Even though more than 100 &bgr;-Ta grains are found under a single Cu grain, the Ta grains under a Cu grain have long range in-plane texture with [330] direction aligned parallel to the [220] direction of Cu. This orientational coincidence is explained by the heteroepitaxial relationship between the hexagonal close-packed atomic array in Cu (111) plane and the pseudohexagonal configuration of &bgr;-Ta atoms in (002) plane with a misfit strain of 7.6&percent;. ©1997 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.119439

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Gallium nitride films have been grown on (0001) sapphire substrates by chemical beam epitaxy (CBE) using triethyl gallium (TEG) and ammonia(NH3)precursors. Prior to the CBE epi-GaN layer growth, electron cyclotron resonance plasma-assisted metal-organic molecular beam epitaxy was utilized to deposit a nucleation layer at lower temperatures. The crystallinity of CBE-grown GaN films was found to be strongly growth–temperature dependent. The degree of crystallinity was correlated with the surface carbon composition as measuredin situby mass spectroscopy of recoiled ions. The optimum growth–temperature range for CBE GaN growth was found to be between 800 and 825 °C. Within this narrow window, thin films with streaky two-dimensional reflection high-energy electron diffraction patterns and good photoluminescence properties were obtained. The surface rms roughness, as measured by atomic force microscopy, was as low as40 Å/1 &mgr;m2for the highest quality thin films; lattice-resolved images supported the deposition of crystalline GaN revealing hexagonal structures with the spacing anticipated for GaN. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120250

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the design, fabrication, and testing of novelYBa2Cu3O7−&dgr;/SrTiO3/LaAlO3(YBCO/STO/LAO) andAu/SrTiO3/LaAlO3(Au/STO/LAO) coupled microstrip line phase shifters (CMPS). These CMPS were tested at frequencies within the Ku and K bands (12–20 GHz), at temperatures from 24 to 77 K, and at dc voltages(Vdc)from zero to 350 V. A relative insertion phase shift (&Dgr;&fgr;) of 390° was measured for an eight-element YBCO/STO/LAO CMPS atVdc=350 V,16 GHz, and 40 K. At 77 K, a&Dgr;&fgr; ∼260°was obtained for the CMPS at the same bias and frequency. Both results correspond to an effective coupling length of 0.33 cm. At both temperatures, the phase shifter exhibits a figure of merit of∼30°/dB.To our knowledge, these are the best results published so far at these frequencies where miniaturization, insertion loss, and phase delay are key considerations. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120251

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The hopper shaped {111} face frequently observed in cubo octahedral crystallites of diamond has been analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The diamond was grown via hot filament assisted chemical vapor deposition with a feed gas composition of 1&percent; methane in hydrogen. The SEM images of these crystallites show that the {100} faces are usually flatter than the {111}. The hopper shaped {111} faces have been imaged using the tapping mode of the AFM and the angles between planes and their orientations determined. The planes comprising the hoppered {111} face were found to belong to the {221} and {331} family. The implications of the presence of higher index planes as well as other growth features on the growth mechanisms involved are presented. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120282

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Synchrotron radiation photoelectron spectroscopy combined with scanning electron microscopy (SEM) and gravimetry has been used to study GaAs (100) surfaces treated with a neutralized(NH4)2Ssolution. Compared to the conventional basic(NH4)2Ssolution treatment, a thick Ga sulfide layer and strong Ga–S bond were formed on the GaAs surface after dipping GaAs wafers in a neutralized(NH4)2Ssolution. Gravimetric data show that the etching rate of GaAs in the neutralized(NH4)2Ssolution is about 15&percent; slower than that in the conventional(NH4)2Ssolution. From SEM observation, fewer etching pits with smaller sizes were found on the neutralized(NH4)2S-treated GaAs surface. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120252

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Semi-insulating SI GaAs samples from a zone refined crystal were irradiated with high energy protons (24 GeV/c, fluences up to1.64×1014 p/cm2). Optical spectra in transmittance and reflectance were accurately measured in the energy range of 0.6–1.4 eV to determine, through the absorption coefficient, the concentrations of both neutral and ionized EL2 defects as a function of the proton fluence. Both these concentrations have been shown to increase linearly with the proton fluence; this behavior well explains the remarkable decrease of the charge collection efficiency observed in proton irradiated GaAs detectors at doses associated with high luminosity beams at a new particle collider accelerator (e.g., the LHC at the CERN laboratory). ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120253

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present a new magnetoelectronic device consisting of a &mgr;m-scale semiconductor cross junction and a patterned, electrically isolated, ferromagnetic overlayer with in-plane magnetization. The large local magnetic field emanating from the edge of the thin ferromagnetic film has a strong perpendicular magnetic component,B⊥(r),which induces a Hall resistance,RH,in the microjunction. External application of a weak in-plane magnetic field reverses the magnetization of the ferromagnet and with itB⊥(r),thus modulatingRH.Our data demonstrate that this strong “local” Hall effect is operative at both cryogenic and room temperatures, and is promising for device applications such as field sensors or integrated nonvolatile memory cells. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120254

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The microstructure of Al films deposited on GaAs(100)2×4surfaces through chemical vapor deposition from dimethylethylamine alane in the 100–160 °C temperature range exhibits a dominant (111) texture which is not encountered in evaporated films. Such a texture has been associated with enhanced electromigration resistance in related systems. Growth of (111)-oriented grains is observed when the deposition rate is limited by the surface reaction of the impinging precursor molecules, while at higher temperatures (160–400 °C) only the conventional texture is observed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120255

出版商:AIP    

年代:1997

数据来源: AIP