摘要:

Nanostructured Cu‐9.5Ni‐4.0Sn‐7.5P samples represent a polycrystal microstructure of nanometer‐sized &agr;‐Cu and Cu3P crystallites for crystallite sizes less than 20 nm and of nanometer‐sized &agr;‐Cu, Cu3P, and Ni2P crystallites for crystallite sizes greater than 20 nm. The specific heat values between 300 K and 400 K for the nanostructured sample with crystallite size of 10 nm are about 20% higher than for the amorphous sample and about 40% higher than for the coarse‐grained sample. The hardness of the nanostructured sample with crystallite size of 10 nm is 30% higher than that of the amorphous sample and 110% higher than that of the coarse‐grained sample. The variation in hardness with the crystallite size for the nanostructured samples follows the Hall‐Petch relationship. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113353

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The scanning tunneling microscope (STM) has been used to fabricate grooves a few nm wide at room temperature by extracting atoms one by one from the Si(111)7×7 surfaces. When the direction of modification is parallel to the basic vector of Si(111)7×7 surfaces, grooves formed by such a process have atomically straight edges and lateral features as small as one 7×7 unit cell wide. The critical current under various voltages for fabricating grooves is measured. The modification mechanism is discussed based on the experiment data in this letter. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113354

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new process for polishing diamond is presented. The reaction and polishing take place at the interface of an oxygen superionic conductor (yittria‐stabilized zirconia) and the diamond. Oxygen anions are transported to the interface under the influence of an electric field and react with the diamond. It is believed that a volatile product of CO and/or CO2is formed during the polishing. The process takes place at moderately low temperatures, without mechanical motion, and can be accomplished in ambient air, making it an attractive and useful method. In addition, the process is damage‐free with no polishing residue, as has been determined by energy dispersive x‐ray analysis. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113355

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The orientation effect of liquid crystal and polyimide molecules on the Langmuir–Blodgett (LB) films was studied. The orientation degree of polyimide chain in the LB films is less than that in the strong rubbing films. This result may be due to bad linear structure of polyimide. The 9 or 11 LB film layers may well align liquid crystals, but the orientation effect of liquid crystals on the polyimide LB films is worse than that on the strong rubbing films. The surface azimuthal anchoring energy of liquid crystals on the polyimide LB films was measured by a torque balance method proposed by our group. The intermolecular interaction between liquid crystal and polymer molecules is considered to be very important for aligning liquid crystals on the polymer surface. ©1995 American Institute of Physics.   

ISSN:0003-6951    

DOI:10.1063/1.113356

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Passivation of the GaAs (100) surface by self‐assembled monolayers of octadecylthiol (ODT) has been studied using inelastic light scattering as a probe of the near‐surface electronic structure. Application of the ODT self‐assembled monolayers reduces the width of the depletion region at the surface of GaAs resulting in a reduction of the surface band bending, and the electron scattering time is increased as well. The ODT passivated surfaces are more stable to environmental degradation, over time and under temperature stress, than inorganic sulfide treated surfaces which have been reported. Organic thiol passivation may provide an attractive alternative to inorganic sulfide protocols for reduction of surface recombination velocities in III–V devices. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113357

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The electron paramagnetic resonance (EPR) spectrum of the neutral phosphorus vacancy has been observed in as‐grown ZnGeP2during illumination at liquid‐helium temperatures. Without illumination, this donor is a nonparamagnetic singly ionized phosphorus vacancy (VP+center). Either above‐band‐gap light (514.5 nm) or below‐band‐gap light (632.8 nm) can produce the paramagnetic neutral state (VP0center) of the donor. Principal values of thegmatrix for the neutral donor are 1.944, 2.046, and 2.223. The angular dependence of the EPR spectrum suggests that the unpaired spin is unequally shared by two of the zinc ions neighboring the phosphorus vacancy. These phosphorus vacancies are the dominant donor in this highly compensated material, while the previously reported zinc vacancies are the dominant acceptor. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113358

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Electron cyclotron resonance etch rates for GaN, InN, and AlN are reported as a function of temperature for Cl2/H2/CH4/Ar and Cl2/H2/Ar plasmas. Using Cl2/H2/CH4/Ar plasma chemistry, GaN etch rates remain relatively constant from 30 to 125 °C and then increase to a maximum of 2340 A˚/min at 170 °C. The InN etch rate decreases monotonically from 30 to 150 °C and then rapidly increases to a maximum of 2300 A˚/min at 170 °C. This is the highest etch rate reported for this material. The AlN etch rate decreases throughout the temperature range studied with a maximum of 960 A˚/min at 30 °C. When CH4is removed from the plasma chemistry, the GaN and InN etch rates are slightly lower, with less dramatic changes with temperature. The surface composition of the III–V nitrides remains unchanged after exposure to the Cl2/H2/CH4/Ar plasma over the temperatures studied. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113359

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A comprehensive characterization has been made of the static and dynamical response of conventional and multiple quantum well (MQW) avalanche photodiodes (APDs). Comparison of the gain characteristics at low voltages between the MQW and conventional APDs show a direct experimental confirmation of a structure‐induced carrier multiplication due to interband impact ionization. Similar studies of the bias dependence of the excess noise characteristics show that the low‐voltage gain is primarily due to electron ionization in the MQW‐APDs, and to both electron and hole ionization in the conventional APDs. For the doped MQW APDs, the average gain per stage was calculated by comparing gain data with carrier profile measurements, and was found to vary from 1.03 at low bias to 1.09 near avalanche breakdown. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113360

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Capacitance spectroscopy is used to determine the allowed energy levels for electrons and holes in InAs self‐assembled quantum dots embedded in GaAs. Using this technique, the relative energy of the electron and hole states is measured with respect to their respective energy band minima in the GaAs. This allows the construction of an energy level diagram for these quantum dots which correlates well with previously observed photoluminescence data. By tuning the device geometry, a fine structure in the electron ground state is revealed and attributed to Coulomb charging effects. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113361

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

All‐perovskite ferroelectric field effect transistors (FET) are proposed, and switching behaviors of the prototype devices having a (Pb,La)(Zr,Ti)O3as a gate insulator and a La1.99Sr0.01CuO4as a channel layer were demonstrated. Marked improvements in device performances were obtained as compared with the previous ferroelectric FETs. Namely, the present device was written and erased at an operating voltage of 7 V with a pulse width of less than 1 ms, yielding resistance modulation up to about 10% and retaining its memory for more than 10 days at room temperature. Examinations show that the switching speed was limited by a delay constant and can therefore be improved up to 1 &mgr;s, and that the memory retention may not be limited by an intrinsic ferroelectric instability as previously suggested. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113362

出版商:AIP    

年代:1995

数据来源: AIP