摘要:

Antiferroelectric PbZrO3thin films have been fabricated by a multi‐ion‐beam sputtering technique at a substrate temperature as low as 415 °C. Single crystal perovskite PbZrO3films oriented along theaaxis could be epitaxially grown on (100)MgO, (100)Pt/MgO substrates using a PbTiO3buffer layer. The PbZrO3films achieved high dielectric constants of about 400, which are almost 2.4 times larger than that of bulk PbZrO3. The measurements ofD–Ehysteresis loops and Curie temperature demonstrated the antiferroelectric to ferroelectric phase transition of PbZrO3films with a thickness of 1770 A˚, while for PbZrO3films of 875 A˚ the phase transition could not be clearly observed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113544

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

High‐quality PbTiO3thin films have been grown on LaAlO3substrates by metalorganic chemical vapor deposition, using purified metalorganic precursors titanium‐iso‐propoxide and tetra‐ethyl‐lead. The results of the cross‐section scanning electron microscopy and x‐ray diffraction (XRD), including theta and phi scan, show that the films are epitaxy, andadomains andcdomains may align alternately in the thin films. The experiments of high‐temperature XRD reveal the nature of the phase transition of grown PbTiO3thin films from tetragonal to cubic phase. The transition temperature is around 460 °C which is far lower than that of bulk PbTiO3and the thin films deposited on fused quartz substrates. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113545

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The transmission properties of gadolinium scandium gallium garnet doped with chromium and neodymium have been studied during and after a 20 ns high‐energy x‐ray pulse. Gain is observed in the transmission which indicates a small signal gain of 0.175/cm. About 5% of the absorbed dose is converted to inversion, which is comparable to flash‐lamp‐pumped inversion. The small signal gain scales with dose. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113546

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Modifications induced by laser heating of C60single‐crystal surface under different conditions are examined by scanning electron microscopy. The fullerite surface is etched in the presence of oxygen, whereas no substantial change is seen under inert atmosphere. The fragments, obtained after the oxygen‐induced disintegration of fullerene, form a material with a nanostructure similar to amorphous carbon. Three‐dimensional microstructures are produced depending on laser annealing conditions. Oxygen in the irradiated region substantially increases, according to energy dispersive x‐ray spectroscopy of the surface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113547

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Thin films of (Pb1−xLax)(Zr1−yTiy)1−x/4O3(5/70/30) were depositedinsituonto (100) Si, Pt/Ti/SiO2/Si, and SrTiO3/Si substrates by pulsed laser deposition from stoichiometric targets and subsequent annealing. Films grown on SrTiO3/Si exhibited desired perovskite structure. On (100) Si and Pt/Ti/SiO2/Si substrates, films exhibited a perovskite‐pyrochlore mixed structure. Apparent Pb deficiency at the near‐surface region was observed. Films deposited at different substrates showed variations in Si content. The buffering effect of SrTiO3was evidenced using x‐ray diffraction and secondary ion mass spectrometry analyses. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113548

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The metalogranic vapor‐phase epitaxy (MOVPE) growth of site‐controlled nanowhiskers having a single preferential growth direction is accomplished by using a SiO2window mask. A small window size (200×200 nm in this experiment) is essential for growing a single whisker from a single Au‐ seed cluster formed inside each window of the mask. The presence of the SiO2mask greatly influences the MOVPE growth process, especially the growth direction and resultant diameter of the whiskers. This influence may be due to surface migration of the source materials or source gas diffusion near the surface from the masked region to the window region. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113549

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In this letter we show that contrary to recent suggestions the hot carrier distribution at energies greater than the maximum available from the electric fields within a device does not take the form exp(−&egr;/kTL), whereTLis the lattice temperature. The effective temperature is shown to be typically 1.35TLclose to the supply energy, only approachingTLat energies well above that available from the electric field. Our results are obtained by solving the one‐dimensional Boltzmann transport equation using a novel hybrid Monte Carlo/iterative technique. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113550

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Superlattices of 100‐period InxGa1−xAs (15 A˚)/GaAs(100 A˚) grown on GaAs (100) substrates by molecular beam epitaxy were studied by using large angle x‐ray scattering techniques. In contrast to the usual superlattice satellite peaks corresponding to structural periodicity along the growth direction, unusual satellite peaks in the lateral direction parallel to the sample surface were observed in a sample withx=0.535 grown at 480 °C, indicating an in‐plane ordering. This result is confirmed by high resolution transmission electron microscopy observations that thickness modulation in the InxGa1−xAs layers gives rise to long‐range lateral periodic arrays of clusterlike microstructures with spacing on the order of a few hundred angstroms. This thickness modulation is found to occur only in the [110] direction, thus the material can be viewed as a somewhat disordered array of grown‐in parallel quantum wires. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113551

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

&bgr;‐SiC (3C–SiC) films were deposited on silicon substrates by electron cyclotron resonance chemical vapor deposition from SiH4/CH4/H2mixtures at 500 °C. The crystalline structure and chemical composition of the deposited film were found to depend on the SiH4/CH4flow ratio. With a sufficient energy supply from microwave power and a SiH4/CH4flow ratio of 0.5 and lower, stoichiometric SiC could be deposited on Si substrates. Microcrystalline &bgr;‐SiC was grown at a SiH4/CH4flow ratio of 0.5, whereas amorphous SiC was obtained at the SiH4/CH4flow ratios lower than 0.5. When the SiH4/CH4flow ratio was above 0.5, only polycrystalline Si could be deposited. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113552

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Persistent photoconductivity has been observed at low temperatures inthin,unintentionallydopedGaInP/GaAs/GaInP quantum wells. The two‐dimensional electron gas was studied by low field Hall and Shubnikov–de Haas effects. After illumination with red light, the electron concentration increased from low 1011cm−2to more than 7×1011cm−2resulting in an enhancement of both the carrier mobility and the quantum lifetime. The persistent photocarriers cannot be produced by DX‐like defects since the shallow dopant concentration in the GaInP layers is too low to produce the observed concentration. We suggest that the persistent carriers are produced by photoionization of deep intrinsic donors in the GaInP barrier layer. We also report observation of a parallel conduction path in GaInP induced by extended illumination. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113553

出版商:AIP    

年代:1995

数据来源: AIP