摘要:

Fe–N films were prepared by ion‐beam‐assisted deposition at different N/Fe atomic arrival ratios to the substrates. Films consisted of nitrogen‐rich &agr;‐Fe and different phases of iron nitrides including &zgr;‐Fe2N, &egr;‐Fe2‐3N, and &ggr;′‐Fe4N were formed. The phase composition of Fe–N films was found to depend sensitively on the N/Fe atomic arrival ratio and deposition temperature. The magnetic properties of the films mainly depends on phase composition. It was found that nitrogen‐rich &agr;‐Fe films exhibited higherMsthan that of the pure iron film, and theirMscould be increased further by vacuum annealing at relatively low temperatures. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360021

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Magnetic force microscope (MFM) studies of high‐density thin‐film recording media have been performed in the presence of an applied magnetic field. In particular, the erasure behavior of bit transitions in the media have been investigated. For these studies a compact, high‐field dc magnet has been constructed that fits the laser head of a Nanoscope III multimode microscope. Because of space constraints and concern over thermal drifts which could affect the stability of the MFM, a rotating permanent magnet was used instead of an electromagnet. The magnet is mounted in a yoke which guides varying amounts of flux to the sample. This was used to observe the erasure of bits in a magnetic hard disk. The applied field also magnetized the MFM cantilever, making it possible to magnetically characterize both the sample and the probe. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360022

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The current response of water and sodium chloride solutions subjected to high amplitude electric fields of sub‐microsecond duration has been investigated. The prebreakdown current‐voltage relationship for these liquids is found to be nearly linear for the fields considered and therefore described by a resistance, R. For constant concentration, R does not extrapolate to zero as the gap width, d, goes to zero, suggesting the presence of a high resistivity sheath near the electrodes. Estimates for the sheath parameters (electric field in the sheath, Es, width, dl, formation time, tl, and ion density, ns) are obtained from these measurements. The contribution of electronic and ionic currents to the breakdown probability has been assessed from the power input to the liquid during the pre‐breakdown phase. For applied fields with sub‐microsecond duration, the input power is primarily due to electron field emission currents whose magnitude is a function of the field in the ionic sheath. For the parameters investigated, ionic currents are found to play a secondary role in these time scales. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360023

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Silicon oxide, SiOx(1≤x≤2), formed by molecular‐beam deposition (MBD) has many attractive optical, electrical, mechanical, and chemical properties which make it a suitable dielectric for many semiconductor device applications. It can be thermally evaporated at a much lower temperature than Si, SiO2, or Si3N4and it condenses on cooler surfaces in uniform and adherent stoichiometric SiO (x=1) films when evaporated in high vacuum. At low deposition rates and at high pressures of oxygen, SiOx(1≤x≤2) films result. This allows variation of refractive index, stress, and other properties withx. MBD‐SiOxfilms are insensitive to moisture absorption. A high quality thin film of SiO2formed on the surface of SiOx, when exposed to an oxidizing ambient, protects the SiOxfilm underneath from the environment. Dielectric breakdown strength of the SiO films is comparable to that of other high quality deposited dielectrics. In general, the SiO (x=1) films are under tensile stress of <100 MPa, which is significantly lower than that observed in other dielectric films. Introduction of a small amount of oxygen during deposition reduces the tensile stress; at an O2pressure of 5×10−7Torr and above, the films are in compression. This allows the tunability of stress, and deposition of films essentially free from stress. Furthermore, both Si and SiO have similar values of the linear thermal expansion coefficients (average values between 23 and 350 °C: 3.37×10−6and 2.7×10−6 °C−1, respectively). As a result, SiOx/Si films develop little stress during thermal cycling. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360024

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have carried out interface plasmon polariton (IPP) and specular x‐ray reflectivity studies of thesamemultilayer structure containing a thin metallic silver film and a thin (100–600 A˚) smectic C* ferroelectric liquid crystal (FLC) film on a glass substrate. An additional thin nylon layer sandwiched between these two films is essential to improve the smectic FLC alignment and its stability. The specular x‐ray reflectivity after each stage of layer deposition provides information on the thickness and the electron density of the individual layer. Particularly, this technique allows for the determination of the amplitude and the phase of the electronic density modulation (i.e., the smectic order parameter) of the FLC film. We demonstrate that the x‐ray results are essential for the determination of the complex dielectric functions of the FLC film from the shape and the angular position of the IPP resonance. Generally, we have found that for samples with a relatively large smectic order parameter the IPP resonance can be best fitted assuming an anisotropic dielectric tensor and the presence of domains in the FLC film. For well ordered smectic C* films at room temperature, the anisotropy of the dielectric tensor is slightly higher compared to the bulk value and shows a tendency to increase with the decrease of the film thickness in ultrathin films. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360025

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report on the growth of high quality pseudomorphic InAsxP1−x/InP single and multi‐quantum well (MQW) structures by solid source molecular beam epitaxy, using valved cracker sources to accurately control the group V ratio. A series of MQW’s grown in ap‐i‐nconfiguration covering the 1.0–1.30 &mgr;m wavelength showed intense narrow room temperature photoluminescence (PL) and extremely narrow 10 K PL linewidths (≤8 meV). Devices fabricated from these structures exhibited low reverse dark currents (<10 nA at 25 V) which increased as the strain within the structure increased. These results confirm the suitability of InAsxP1−x/InP for optoelectronic devices in this wavelength range. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360026

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Aged porous silicon layers (∼1 &mgr;m thick) have been characterized both by optical spectroscopy (Raman scattering and photoluminescence) and by nuclear surface techniques (Rutherford backscattering, elastic recoil detection, and nuclear reaction analysis). Samples with 85% and 70% porosity were analyzed after exposure to air for 1 month. Both these aged porous silicon layers emit visible light, but their luminescence shows dissimilar spectral features while their Raman scattering suggests a dissimilar microstructure. Chemical analyses indicate the presence of carbon and hydrogen at the porous surface, besides a surprisingly different oxygen concentration. A correlation between the structural and compositional results is attempted to account for the observed light emission spectra. In particular, the relative blue shift of the luminescence peak of sample with lower porosity is attributed to the stronger consumption of silicon nanocrystals operated by the silicon oxide formation during the aging process. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360027

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The properties ofa‐SiOx:H thin films deposited at low temperature (∼ 50 °C) in a low energy magnetron rf plasma system with Ar/SiH4/O2gas mixtures are investigated. In the low pressure regime (about 5 mTorr reactive gases), the surface reaction dominates in the film formation process. As the partial pressure ratio (ROS) of oxygen to silane increases, the Si‐H related vibrational modes gradually disappear, and the film becomes stoichiometric SiO2forROS≥1. High quality oxide film can be deposited due to the low pressure environment and the plasma promoted surface process. In the high pressure regime (tens of mTorr) the deposited SiO2films contain fine particles (tens of nanometer in size) and are porous (15% void) due to the gas phase homogeneous reaction and aggregation. The infrared absorbance spectra with normal and oblique incidence imply different origins of the half width and the shoulder intensity of the 1070 cm−1Si‐O(s) mode. In comparison with the low pressure dense films, the narrow half width of the high pressure film may be caused by the more ordered local structure which has a narrower distribution of bond angle and length, while the large shoulder intensity may be dominated by the larger (fine particle size) scale disorder. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360028

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoluminescence (PL) studies of SF6/O2plasma‐induced defect formation inn‐type silicon samples are reported. Ion bombardment of the silicon surface during the SF6reactive‐ion etching (RIE) is shown to introduce defects giving rise to a broad PL band in the 0.70–1.00 eV spectral range and to the carbon‐relatedCandGlines. The role of oxygen during SF6/O2RIE on the photoluminescence observed is analyzed. It is argued that oxygen contamination enhances the formation of PL centers via the creation of extended defects, such as oxygen precipitates. A lattice contraction nearby these extended defects is suggested to be responsible for the observed splitting of theCandGlines as well as the shift of the phosphorous bound exciton line detected after SF6/O2RIE. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360711

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The effect of laser cutting on the structure of a chemical vapor deposited diamond film has been investigated by cathodoluminescence (CL) in the scanning electron microscope. The variation of particle morphology and CL spectra as a function of the distance to the cutting edge is described and possible laser induced structural changes are discussed. At the damaged region total CL emission increases and nitrogen‐vacancy centers are detected. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359960

出版商:AIP    

年代:1995

数据来源: AIP