摘要:

The effect of substrate bias voltage was investigated for bias‐enhanced diamond nucleation pretreatments of diamond thin films in a microwave plasma chemical vapor deposition reactor. A critical bias voltage of approximately −200 V was observed for nucleation density enhancement from ∼104cm−2to ∼1010cm−2. Furthermore, the nucleation density under bias conditions was five orders of magnitude lower for a small silicon region electrically isolated from the otherwise negatively biased silicon substrate. These results confirm that bombardment of the substrate by energetic cations plays a significant role in the diamond nucleation mechanism during bias pretreatments. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113621

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Epitaxial and preferentially oriented Bi4Ti3O12thin films were grown using pulsed laser deposition on LaAlO3(001) and Al2O3(0001) substrates, respectively, with La0.5Sr0.5CoO3bottom electrode layers. X‐ray diffraction analysis shows that the Bi4Ti3O12films are grown (001) and (104) oriented on La0.5Sr0.5CoO3(001)/LaAlO3(001) and La0.5Sr0.5CoO3(111)/Al2O3(0001), respectively. These growth behaviors can be explained using arrangements of oxygen ions. Cross‐sectional scanning electron microscopy shows that microstructures of the heterostructures depend on the substrates. It is found that the growth behaviors and the microstructure affect leakage current behaviors of the Bi4Ti3O12layers. Ohmic and space‐charge‐limited conduction mechanisms are used to explain leakage current behaviors of the Bi4Ti3O12film on La0.5Sr0.5CoO3/LaAlO3(001) and La0.5Sr0.5CoO3/Al2O3(0001), respectively. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113622

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The entropy of fusion of a metal consists of the configurational and vibrational entropies. A formula is presented to evaluate the configurational entropy by assuming an amorphous phase to be a frozen liquid that has lost the configurational entropy but still maintains the vibrational entropy of the corresponding liquid. The magnitude of the configurational entropy may provide information on the nature of liquid structures. The evaluation requires the enthalpy of the amorphous phase in addition to those of the liquid and crystalline phases. The illustrative evaluation on the Ni24Zr76alloy shows that &Dgr;Sconfis approximately 1kper atom, wherekis the Boltzmann constant, which suggests some degree of clustering of atoms in the liquid. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113623

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The fading characteristics of KCl:Eu2+(150 ppm) thermoluminescent crystals is determined. It is shown that the fading cannot be correctly measured without taking into account the phenomenon of self‐irradiation of the crystals, due to natural radioactive nuclide40K which is presented in potassium halide dosimeters. The results obtained can be useful in those applications of KCl: Eu2+crystals dealing with long‐time exposures, or low‐dose levels of radiation. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113624

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Single phase chalcopyrite CuInSe2(CIS) phase formation at low temperatures (≊260 °C) is demonstrated by Se vapor selenization of evaporated metal precursors at a pressure of ≊0.3 mbar. The low pressure changes the relative kinetics of selenization of Cu and In due to the modification of the availability of Se reacting species. Consequently, the thermodynamically favorable reaction CuSe+In(1)+Se→CIS proceeds to completion at lower temperatures. This is confirmed by the absence of In2Se3at intermediate pressures (0.5–1.0 mbar). At higher pressures (≊7–10 mbar) and Se flux, simultaneous formation of the equilibrium binaries, CuSe and In2Se3at low temperatures, leads to the formation of CIS through a diffusion limited reaction of the binaries at higher (≥400 °C) temperatures. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113626

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A powder mixture of copper and graphite was dynamically shock‐compressed by a rod‐in‐cylinder method. Structural characterization of the recovered specimen by transmission electron microscopy (TEM) showed the development of fine spherical diamond particles through shock‐induced nuclei formation in the high pressure state and shock‐assisted nuclei growth during unloading to ambient pressure via a solid–liquid–solid (SLS) phase transformation. A 2 &mgr;m large diamond particle was formed via a shock‐induced martensitic path. Quantitative numerical simulation applying the two‐dimensional computation code AUTODYN 2D was conducted to evaluate the pressure conditions during shock loading. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113627

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Passive diamond layers fabricated using chemical vapor deposition can improve thermal conduction in electronic microstructures. The benefit of using diamond depends strongly on the thermal boundary resistance between active semiconducting regions, where heat is generated, and the diamond. Two independent experimental methods measure the total thermal resistance for conduction normal to 0.2, 0.5, and 2.6 &mgr;m thick diamond layers deposited on silicon, providing an upper bound for the effective silicon‐diamond boundary resistance. The data agree with predictions that couple the local phonon scattering rate in the diamond to the grain size. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113625

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Electron transmission in the fundamental transverse mode of an asymmetric double‐stub electronic stub tuner (ADEST) in the ballistic regime is theoretically shown to be a symmetric, almost sine wavelike, periodic function of an offset parameterd, wheredis a measure of the stub asymmetry and is the distance between the lines that bisect the stub and the main wire. The periodic pattern remains quite robust at finite temperatures (≊5 K). This unique multiple folding output characteristic of a single ADEST may conceivably be used for fast, high binary bits analog‐to‐digital conversion. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113628

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The light emitting properties of ZnS/ZnSe and ZnSTe/ZnSe strained II–VI superlattices are investigated. Room‐temperature stimulated emission by photopumping in the deep‐blue spectral region is observed. An upper limit of threshold carrier density required to achieve lasing is estimated to be 3×1018/cm3.The peak of stimulated emission is several tens of meV red shifted from the spontaneous emission peak, suggesting that exciton‐exciton scattering is involved in the stimulated emission process. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113629

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Use of a rapid thermal annealing technique is shown to improve the electrical properties of metal‐ferroelectric BaMgF4‐silicon capacitors. The fluoride film was deposited in an ultrahigh vacuum system at a substrate temperature of 300 °C. A postdeposition annealing was conducted for 10 s at 600 °C followed by subsequent annealing for 5 s at 750 °C. The results were found out to increase the resistivity of the ferroelectric BaMgF4film from a typical value of 1–2×1011&OHgr; cm before the annealing to about 5×1013&OHgr; cm at 1 MV/cm and reduce the interface state density of the BaMgF4/Si interface to about 8×1010/cm2 eV. Ferroelectric hysteresis measurements using a Sawyer–Tower circuit yielded remanent polarization and coercive field values of about 0.26 &mgr;C/cm2and 315 kV/cm, respectively. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113703

出版商:AIP    

年代:1995

数据来源: AIP