摘要:

Electron paramagnetic resonance (EPR) has been used to identify the primary electron and hole traps responsible for ‘‘gray tracks’’ in flux‐grown KTiOPO4(KTP). Ionizing radiation (x rays) was used to produce the gray‐track effect. During an irradiation at 0 °C, a broad absorption band peaking near 500 nm is introduced, the EPR spectra from a series of Ti3+centers appear, and the dominant EPR spectrum associated with Fe3+ions decreases significantly. Following the irradiation, the decay of the optical absorption and the Ti3+centers, along with the growth of Fe3+centers, were monitored over a period of 20 h at room temperature. Changes in the EPR spectra of the Ti3+and Fe3+centers during the anneal correlated with the decay of the induced optical absorption (i.e., gray track). These results demonstrate that Fe3+centers are the primary hole trap and Ti4+‐VOcomplexes are the primary electron trap responsible for gray track formation in flux‐grown KTP crystals. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113376

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A phase distortion method is applied to examine the optical nonlinearity in titanium dioxide single crystal. The two‐photon absorption coefficient obtained agrees with that reported previously, while the nonlinear index of refraction is larger than that predicted theoretically by a factor of 10. One of the reasons for the discrepancy is given as the applicable limit of the simple theory in which a two‐parabolic band model has been assumed in the analysis. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113377

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Charge drift mobilities of five oxadiazole derivatives doped in polycarbonate (PC) were evaluated with the time‐of‐flight technique. It is demonstrated that oxadiazoles incline to having electron‐transport characteristics. In particular, an oxadiazole with naphthyl substituent (BND) was found to possess high potential of electron transport; the electron drift mobility of 50 wt % BND doped PC was 2.2×10−5cm2 V−1 s−1at an electric field of 7.5×105V cm−1at room temperature. In addition, incorporating strong electron‐releasing substituents into oxadiazoles was demonstrated to add hole transport characteristics to oxadiazoles. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113378

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Plasma polymer thin films with embedded silver particles (5‐50 nm) were irradiated by a small focussed electron beam of 10 kV. Before and after irradiation the films were investigated by transmission electron microscopy (TEM) to characterize the microstructure given by size and shape of the embedded silver particles. The changes of the microstructure after the electron beam irradiation were limited to small lines (<2 &mgr;m). Most changes were coalescence of the silver particles. Furthermore, after increased irradiation time and higher energy input areas nearly free of silver particles but without destruction of the plasma polymer matrix were found. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113379

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

It is shown, by numerical analysis, that piezoelectric interfacial waves guided by a conducting plane embedded in a lithium niobate crystal exist in ∼6% of the volume of space of three Euler angles describing the plane orientation and the wave propagation direction with respect to crystallographic axes. Example wave solutions are presented. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113380

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The effect of atomic hydrogen on thin deposited layers of amorphous silicon was studied. Amorphous silicon layers less than 10 nm thick were first deposited from fluorinated precursors. These layers were then exposed to an atomic hydrogen flux. The amorphous layers quickly relaxed to a crystalline structure. Thick films of high crystalline content were prepared through sequential repetition of the deposition and hydrogen exposure process (layer‐by‐layer technique). The relaxation process was studied by real timeinsituellipsometry and infrared measurements. The relationship between substrate temperature, amorphous layer thickness, hydrogen exposure time, and structure was determined. A new model in which hydrogen acts to ‘‘liquify’’ the subsurface region by breaking Si–Si bonds is suggested. From the ‘‘liquidlike’’ state the subsurface relaxes to its most thermodynamically stable constituents; during relaxation, crystalline silicon is formed with effluence of SiH4, SiFxH4−x, and SiF4vapors. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113381

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Amorphous carbon (a‐C) films grown by vacuum‐arc deposition techniques contain substantial amounts of compressive, residual, growth stress (over 10 GPa). The magnitude of the stress can be controlled by changing the incoming energy of the ions. It is observed that stress shifts the Raman scattering feature in these films to higher frequency by as much as 20 cm−1. The Raman spectra of adhering and delaminated films are used to measure the magnitude of the stress‐induced shift, which is −1.9 cm−1/GPa for compressive biaxial stress. The observed value is compared to that expected from disordered diamond and graphite structures. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113382

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Phonon replicas in the photoluminescence spectra of a direct gap AlxGa1−xAs alloy have been observed. The GaAs‐like transverse optical and longitudinal optical as well as AlAs‐like longitudinal optical modes were observed at the &Ggr;‐point. We also observe what we believe to be the longitudinal acoustical phonons at theL‐point in the Brillouin zone. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113383

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The evolution of surface roughness and the subsequent plastic relaxation mechanisms have been studied by transmission electron microscopy (TEM) as a function of the thickness of highly strained In0.30Ga0.70As layers on GaAs(001). The following stages have been observed: formation of coherent islands, coalescence of islands, and nucleation of dislocations at the troughs of the surface ripples. Dislocations are thus systematically generated where the highest stress concentrations are expected, according to recent theoretical predictions. It is the first time such a plastic relaxation mechanism has been observed in highly strained semiconductor heterostructures. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113384

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Reactive deposition epitaxial growth of &bgr;‐FeSi2film on Si(111) has been studied byinsituobservation of reflective high energy electron diffraction combined withexsituAuger electron spectroscopy depth profile analysis. The direct phase formed at the top surface after iron coverage has been determined to be mixture Fe3Si and Fe5Si3, FeSi, and &bgr;‐FeSi2, respectively, according to the results of different deposit temperature. Diffraction patterns as well as the depth profile for the Fe/Si ratio have been discussed. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113385

出版商:AIP    

年代:1995

数据来源: AIP