摘要:

We report the successful deposition of highlyc-axis oriented CaBi2Nb2O9(CBN) thin films directly onp-type Si(100) substrates by pulsed laser deposition. The CBN thin films exhibited good structural, dielectric, and CBN/Si interface characteristics. The electrical measurements were conducted on CBN thin films in a metal–ferroelectric–semiconductor (MFS) capacitor configuration. The typical measured small signal dielectric constant and the dissipation factor at a frequency of 100 kHz were 80 and 0.051, respectively. The leakage current of the MFS capacitor structure was governed by the Schottky barrier conduction mechanism and the leakage current density was lower than 10−7A/cm2at an applied electric field of 100 kV/cm. The capacitance–voltage measurements on MFS capacitors established good ferroelectric polarization switching characteristics. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118587

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

For bulk ceramic materials, small substitutions ofAl2O3inTa2O5are shown to cause a moderate enhancement of the dielectric constant. For compositions near 0.95Ta2O5–0.05Al2O3,the temperature coefficient of the dielectric constant at 20 °C dramatically decreases, from more than 200 ppm/°C for pureTa2O5to less than 20 ppm/°C. The quality factors(Q)at 1 MHz, are 2000–5000. Measurements to 14 GHz at 20 °C show that the dielectric constant is maintained to microwave frequencies, with aQof ∼600 at 5 GHz. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119088

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Linearly polarized laser chemical vapor deposition of liquid crystalline polymer was carried out on the polyimide layer which was exposed with a linearly polarized laser. We used 4[&ohgr;(2-methylpropenoyloxy)hexyloxy]-4′-cyanobiphenyl as a source of polymer film and a KrF excimer laser as an UV laser light source. Before deposition, exposure to a polyimide layer on a substrate was performed through a photomask. In both exposed and nonexposed areas, the film was deposited during laser irradiation. The molecular orientation of the film in the exposed area was perpendicular to the polarization of the exposed laser beam while that in the nonexposed area was parallel to the polarization of a deposition laser beam. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118588

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Spontaneous lateral composition modulation as a consequence of the deposition of a(AlAs)n/(InAs)mshort period superlattice on an InP(001) substrate is examined. Transmission electron microscopy images show distinct composition modulation appearing as vertical regions of In- and Al-rich materials alternating in the [1¯10] projection. The periodicity of the modulation is 130 Å, and is asymmetric. The transmission electron and x-ray diffraction patterns from the structure exhibit distinct satellite spots which correspond to the lateral periodicity. Transmission electron microscopy images show that the individual superlattice layers possess cusplike undulations, which directly correlate with the composition modulation. Composition modulation in this sample appears to be coupled to morphological and compositional instabilities at the surface due to strain. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118589

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Thin film polycrystallineBa0.5Sr0.5TiO3capacitors employing conductive perovskite oxideSrRuO3as a bottom electrode were fabricated on Si substrates by rf-magnetron sputtering. Dielectric constants of these capacitors were observed to be 206, 214, and 146 for 60, 40, and 20 nmBa0.5Sr0.5TiO3(BSTO) thicknesses, respectively. The lowestSiO2equivalent thickness of 0.54 nm was obtained for 20-nm-thick BSTO capacitors; their leakage current density was less than1×10−7 A/cm2for ±1.8 V bias. The cross-sectional transmission electron microscope observation revealed that BSTO andSrRuO3(SRO) formed continuous columnar grains and showed epitaxial growth at the interface of BSTO/SRO within each column; this microstructure of the capacitors was tentatively designated “local epitaxial film.” ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118590

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Predominately hexagonal GaN nucleation layers were grown on sapphire substrate by low pressure metal-organic vapor phase epitaxy. Tilt angles of GaN single crystallites about the normal of sapphire substrate are determined to be in the range from 0° to 5° by using selected area electron diffraction. A small portion of cubic phase of GaN was observed to be selectively distributed in the grain boundary areas and the instantaneous surface state is suggested to play an important role in the nucleation of the Zincblende phase. Phase transition from hexagonal to cubic GaN caused by heavy radiation from ion beam was also noticed. A critical temperature is proposed to exist in forming predominately cubic or hexagonal GaN nucleation layer. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118591

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

By the use of dimethylgermane [(CH3)2GeH2: DMGe], a Si clean surface can be carbonized reproducibly at as low as 650 °C in a gas source molecular beam epitaxy. The initial stage for heteroepitaxy in the 3C–SiC/Si system has been studied with time resolvedin situreflection high-energy electron diffraction (RHEED) analysis. A RHEED pattern from a carbonized layer indicates single-crystalline 3C–SiC without any 3C–SiC twin spots and Ge-related patterns. An activation energy of about 51.1 kcal/mol is obtained in the initial stage of 3C–SiC growth. The successive growth of 3C–SiC layers formed with DMGe is also discussed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118569

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The roughness of the Si(100)/SiO2interface is measured using both surface second harmonic generation (SSHG) and x-ray scattering. A comparison between these techniques shows a clear correlation for typical industrial oxides, despite the techniques being sensitive to differing regions of the roughness spectrum. The SSHG measurements are made using∼10 fs pulses centered at 850 nm and at 80 MHz repetition rate. The short pulses produce a similar signal to noise ratio as earlier measurements, but use much lower average power, thus avoiding possible artifacts such as sample heating. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118592

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The continuous-wave (cw) operation of InGaN multi-quantum-well structure laser diodes (LDs) was demonstrated at room temperature (RT) with a lifetime of 27 h. The threshold current and the voltage of the LDs were 80 mA and 5.5 V, respectively. The threshold current density was 3.6kA/cm2. Longitudinal modes with a mode separation of 0.042 nm were observed under cw operation at RT. When the temperature of the LDs was varied, large mode hopping of the emission wavelength was observed between adjacent quantum well or quantum dot subbands. The carrier lifetime and the threshold carrier density were estimated to be 10 ns and2×1020/cm3, respectively. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118593

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The temporal evolution of Ga and Ca vacuum deposited onto thin films of tris (8-hydroxy quinoline) aluminum (Alq) was studied with valence and atomic core level photoelectron spectroscopy. It was found that Ga, which exhibits weak reactivity with the Alq diffused into the organic at room temperature. Conversely Ca, a significantly more reactive metal, shows strong interaction with the organic surface. Effects of the initial morphology of the deposited materials on diffusivity will be described. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118594

出版商:AIP    

年代:1997

数据来源: AIP