摘要:

Thin nanoporous Si layers were formed onn‐Si(100) in 0.1 M NH4F electrolyte and investigated with field emission scanning electron microscopy and photoluminescence (PL). The microstructure of the electrochemically prepared Si surfaces depended strongly on thepH of the electrolyte. A pebblelike surface structure was formed during anodization atpH 4.5, while nanoporous Si layers were formed at lowerpH. The onset of macropore formation was observed after anodization atpH 3.0. The shape of the PL spectra was found to be practically independent of the nanoporous structure. The results are discussed on the basis of the etch rate of oxidized Si atoms and of the role of surface states for PL. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.114985

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Based on a complete similarity between the plasma waves in a field effect transistor and sound waves, we discuss a possibility of realizing an electronic terahertz oscillator utilizing the excitation of the plasma waves in the two dimensional resonance cavities by adjacent electron flow. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114986

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A large number of epitaxial GaN samples as well as AlN ceramics have been studied by photoluminescence (PL) and PL excitation spectroscopy. In addition to the PL of residual iron, two new bands with zero‐phonon‐lines at 0.931 and 1.193 eV have been observed frequently in GaN. An analysis of the PL bands indicates that they arise from internal transitions within the 3dshell of residual vanadium and chromium impurities. The chromium PL has also been observed in polycrystalline AlN ceramics. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114987

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Strain compensation in SiGe by heavy boron doping was demonstrated. For this purpose, SiGe layers containing up to several percent of boron were deposited using rapid thermal chemical vapor deposition. The strain compensation effect was evaluated by double crystal x‐ray diffraction measuring the difference between the diffraction peak distances of the boron doped samples and a reference sample without boron which can be directly related to the decrease of the lattice constant in Si1−x−yGexBydue to the incorporation of boron. The films were characterized by cross‐sectional transmission electron microscopy (XTEM), Auger electron spectroscopy (AES), and secondary ion mass spectroscopy (SIMS). ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114988

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report the superconducting and structural properties ofa‐axis oriented YBa2Cu3O7−x(YBCO) films as a function of deposition temperature of PrBa2Cu3O7−x(PBCO) template layers. X‐ray diffraction (XRD) analysis revealed the orientation relationship in which thebaxis of the PBCO template layers and theaaxis of the YBCO films were normal to the LaSrGaO4(100) substrate surface. In‐plane aligneda‐axis oriented YBCO films having a zero resistance temperature of 88 K and an anisotropy ratio of resistivity of 11.5 at 275 K were obtained on PBCO template layers deposited at 630 °C among the deposition temperatures ranging from 600 to 650 °C at intervals of 10 °C. The degree of in‐plane alignment of thea‐axis oriented YBCO films which was estimated by the ratio of relative intensity at 90° and 180° in the XRD &fgr; scan of the (102) YBCO peak was 0.5, 0.045, and 0.053 for the films on PBCO templates deposited at 620, 630, and 640 °C, respectively. In conclusion, the deposition temperature of PBCO template layers is critical to fabricate the in‐plane aligneda‐axis oriented YBCO films on LaSrGaO4(100) substrates. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114989

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Insituplanarization of epitaxial films has been demonstrated. This is a critical technology for the processing of any epitaxial multilayer device. Ion beam assisted deposition (IBAD) has been used to planarize patterned yttria‐stabilized ZrO2(YSZ)(001) substrates using YSZ films. X‐ray diffraction measurements have shown that the IBAD YSZ grows homoepitaxially. The IBAD planarization mechanism has similarities to those previously observed for rf bias sputtering. Critical current densities of up to 7×105A/cm2at 77 K have been measured for Ba2YCu3O7−x(BYC) films deposited on planarized patterned YSZ substrates using pulsed laser deposition. In contrast, BYC deposited on unplanarized patterned YSZ substrates did not become fully superconducting for measurements down to 25 K. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114990

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Quantized states are mapped in Ni/Cu/Ni(100) trilayer structures, which are taken as a more accurate rendering of spin valve devices than the bilayers studied previously. We find that an extra Ni overlayer affects the energy of quantized states in the Cu layer, explaining why the magnetic coupling is affected by the thickness of the magnetic layer, and how a phase difference may occur between magnetic coupling oscillations in trilayers and density of states oscillations in bilayers. The potential step that confines electrons to the Cu spacer is determined to be 0.9 eV. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114991

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Thin film multilayer structures consisting of two permalloy layers separated by Ag spacers show little or no giant magnetoresistance in their as‐deposited state, due to a predominantly ferromagnetic interlayer exchange coupling that does not oscillate in sign with variations in the Ag spacer thickness. Upon patterning these films into arrays of dots and other geometries with micron scale features, however, antiferromagnetic coupling and giant magnetoresistance are observed due to magnetostatic interactions between layers that are induced at the edges of the patterns. In this letter we present our experimental results and discuss their relevance as magnetoresistive sensors for magnetic recording heads and other applications. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114992

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Diamond films and islands grown by chemical vapor deposition were implanted with boron, sodium, and carbon ions at doses of 1014–1015/cm2. This structural modification at the subsurface resulted in a significant reduction of the electric field required for electron emission. The threshold field for producing a current density of 10 mA/cm2can be as low as 42 V/&mgr;m for the as‐implanted diamond compared to 164 V/&mgr;m for the high qualityp‐type diamond. When the ion‐implanted samples were annealed at high temperatures in order to anneal out the implantation‐induced defects, the low‐field electron emission capability of diamond disappeared. These results further confirm our earlier findings about the role of defects in the electron emission from undoped orp‐type doped diamond and indicate that the improved emission characteristics of as‐implanted diamond is due to the defects created by the ion implantation process. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114993

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We present a detailed description of the fabrication and operation at room temperature of a novel type of tunnel displacement transducer. Instead of a feedback system it relies on a large reduction factor assuring an inherently stable device. Stability measurements in the tunnel regime infer an electrode stability within 3 pm in a 1 kHz bandwidth. In the contact regime the conductance takes on a discrete number of values when the constriction is reduced atom by atom. This reflects the conduction through discrete channels. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114994

出版商:AIP    

年代:1995

数据来源: AIP