摘要:

Hexaferrite thin films ofBa1−xRxFe12−xNixO19(R=Pr,La) were grown on nonmagnetic garnet substrates by rf sputtering. When deposited at a substrate temperature of 550 °C at rf power density(PDrf)larger than19 W/cm2,the films were completely crystallized, with thecaxis preferentially oriented normal to the film plane. Transmission electron microscopy revealed that the films deposited at lowPDrfwere amorphous but locally contained microcrystallites several nm in size. On the other hand, the films deposited atPDrflarger than20 W/cm2were polycrystalline with a crystallite size as large as 300 nm. Faraday rotation measurements showed that the Ni substitution induced a large negative rotation in the photon energy range of 2.1–2.6 eV. This Ni contribution was predominantly attributed to the crystal-field transition of octahedrally coordinatedNi2+ions lying in the 2 eV range. No contribution byPr3+ions to the Faraday rotation was observed within the photon energy range measured. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366315

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Optical properties of pyrite thin films obtained by iron sulfuration have been studied in samples of different iron thickness (0.12–0.5 &mgr;m) sulfurated at different temperatures in the range 620–770 K. Dispersion values of the optical absorption coefficient and refractive index for wavelengths 0.8–3.0 &mgr;m have been determined by fitting the optical transmission spectra in this range using a multivariable nonlinear program of optimization. Values of absorption background, optical energy gap, and optical film thickness have been obtained for all the samples. These values have been related to microstructural and electrical properties measured in the films. The background absorption is associated with the polycrystalline nature of the samples, as well as the presence of an interface between pyrite film and glass substrate. The optical energy-gap variation found in the samples is attributed to the difference in structure and stoichiometry in the grain and at grain boundaries, respectively. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366316

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Transmission electron microscopy and x-ray diffraction data show that rapid thermal anneals of SrS:Ce thin films enhance grain size and reduce crystalline defects. Electron paramagnetic resonance results suggest that these anneals lead to less variance in the crystal field environments at the nearly cubicCe3+sites along with the formation of another type ofCe3+site believed to involve a nearby Sr vacancy. We suggest that the association ofCe3+sites withVSrshifts the electroluminescence towards larger wavelengths as the symmetry of the activator site is lowered. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366547

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

TheSiO2layers thermally grown on Si wafers were implanted by 130 keV Si ions at liquid nitrogen temperature to a dose of1×1017 ions/cm2.From the as-implanted samples, a visible photoluminescence band centered around 2.0 eV was observed. After postannealing at 1100 °C for 90 min another visible band in the range of 1.7 eV was detected. Interestingly, with increasing thermal annealing time, a blue shift in peak energy and an intensity variation of the 1.7 eV band were observed. A possible interpretation for the observations was discussed in terms of a so-called three-region model. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366317

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Electron emission from a∼100-nm-thick,laser ablated and laser annealed, carbon-doped BN film deposited on polycrystalline diamond was measured at room temperature and at pressures of about1×10−8 Torr.For a 500-&mgr;m-diam extraction electrode, currents of several mA were obtained which corresponds to current densities of>1 A/cm2.At low currents, the current–voltage characteristics follow the classical Fowler–Nordheim behavior. At higher currents, deviations occur which are correlated to a nonlinear BN film resistance which ranges from3×106 &OHgr;to5×104 &OHgr;.For comparison, similar measurements were performed for the polycrystalline diamond film. Current densities of only1 mA/cm2were obtained which is attributed to a much higher sample resistance of about1×109 &OHgr;.©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366318

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Iron nitride films were deposited on Ge(100) wafers by a reactive ion beam sputter deposition of iron in an ammonia atmosphere. The composition and microstructure of these films were monitored by Rutherford backscattering spectroscopy analyses and x-ray diffraction experiments. The magnetic properties of these films were determined by a vibrating sample magnetometer. It was found that Ge(100) substrate is profitable for epitaxial growth of the &agr;′′phase. The optimum ammonia pressure for &agr;′/&agr;′′phase formation was about5×10−4 Torr.The saturation magnetization&sgr;sof each as-deposited Fe–N film is higher than that of a pure iron film. However, the film with the highest &agr;′/&agr;′′phase content did not exhibit the largest&sgr;svalue. The variation of&sgr;sof the Fe–N films during annealing at a temperature of 180 °C in a flowing nitrogen atmosphere was also investigated. It was found that there is no direct relationship between the higher&sgr;svalues and the &agr;′/&agr;′′phase in these Fe–N films. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366319

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the laser crystallization of intrinsic (a-Ge) and hydrogenated (a-Ge:H) amorphous germanium thin films using short, i.e., ns range, laser pulses. The influence of hydrogen on the phase transitions was investigated by monitoring the reflectance of the sample during laser irradiation. We determined the thresholds for melting (36 mJ/cm2)and for surface damage (66 mJ/cm2)of the a-Ge film. In a-Ge:H, hydrogen effuses on a short time scale (10 ns) upon laser irradiation. The effusion leads to the formation of a lifted-off (100 nm thick) crystalline Ge membrane, leaving behind a rough and incompletely crystallized surface. In a-Ge, on the other hand, no surface disruption is observed. The Raman spectra of hydrogenated samples are dominated by stress effects, while those corresponding to non-hydrogenated samples are dominated by crystallite size distribution effects. We also conclude that laser-induced annealing, carried out by applying several pulses with increasing intensity, can be used as a tool for the crystallization of a-Ge:H samples without hydrogen-induced surface damage. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366320

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Microstructures inp-CuInSe2single crystals tailored by a strong electric field have been studied using the methods of local cathodoluminescence, electron-beam-induced current (EBIC), capacitance–voltage (C–V) characteristics, and deep-level transient spectroscopy (DLTS) spectra, and have been considered through a prism of elemental stability in the ternary compound. The shortest-wavelength cathodoluminescence radiation(ℏ&ohgr;m=1.023 eV)is observed from a layer ofntype, the longer-wavelength radiation (ℏ&ohgr;m=1.01and 0.973 eV), fromp-type areas, both aplayer and thep-bulk crystal. The analysis of the spectra has allowed us to attribute experimental features to optical transitions associated with donor and acceptor levels ofVCu,VSe,Cuipoint defects. The capacitance study by theC–Vcharacteristics and DLTS spectra as well as the EBIC test have shown formation of diode-type or transistor-type microstructures. The|ND−NA|concentration profile, thermal activation, and emission energies of 22–25 and 170 meV, and a capture cross-section&sgr;h=2×10−19 cm2of the deep donor level have been obtained for the microstructures. The two-stage resistive model has been considered forp–nandp–n–pjunction formation. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366321

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We propose anannealing methodas an effective way of operating quantum-cellular-automaton (QCA) systems, which are devices for computation that utilize the minimum energy state of electrons in a quantum cell system. A QCA system has an energy function with many local minima and therefore cannot be operated as desired if placed under the conditions of a thermodynamically open system. Accordingly, for successful operation of a QCA system (i.e., making the QCA system converge successfully to its minimum-energy state), we propose a method of operation based on the concept of thermodynamic annealing. We simulate the dynamics of various QCA logic-gate systems operated by this annealing method, and show that data processing in QCA systems can be carried out accurately by means of this annealing method. The applicability of QCA systems to non-Neumann parallel-processing computation is also described. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366322

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Monocrystalline silicon was implanted with 60 keV fluorine and 20 keV boron ions and annealed. Carrier profile, fluorine and boron redistribution, and the parameters ofp+-njunctions were investigated. In ion implanted Si two specific regions were observed in which peculiarities in carrier concentration, resistivity, and F atoms redistribution occurred. It was reasoned that the “under-surface” specific region is enriched with vacancy-type defects while the “amorphous/crystalline(a/c)interface” region is enriched with interstitial type defects. After annealing at a temperature corresponding to the reverse annealing phenomenon, boron atoms were activated in the “under-surface” and deactivated in the “a/cinterface” region. The possibility of PMOS transistor fabrication with ultrashallowp+-njunction (60 nm) and low leakage current byF++B+implantation and low temperature (600–700) °C annealing by using this phenomenon was demonstrated. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366323

出版商:AIP    

年代:1997

数据来源: AIP