摘要:

The transient tunneling current induced by pulsed laser irradiation of a scanning tunneling microscope (STM) tunneling gap was observed to occur over a 100 &mgr;s time scale range in response to a 20 ns duration of the laser pulse. The amplitude of the transient current varies exponentially with laser power, confirming our previous suggestion that thermal expansion of the STM tip is the main source of the transient increase of tunneling current. This thermal expansion mechanism is also supported by the observation of a qualitatively similar variation of the tunneling current during the piezo-driven decrease of the tip-sample separation. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366251

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have demonstrated that the reproducibility of electron beam pulses generated by a high power, cold cathode glow discharge is greatly improved by adding a small continuous keep-alive discharge current. A current of the order of 200 &mgr;A was found to limit the shot to shot current variation to within 1.5&percent;. This stabilization in turn reduces by an order of magnitude the fluctuations of the energy density deposited on the target, demonstrating a reliable energy source for surface treatment. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365723

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The linear thermal expansion coefficients of fused quartz containing 3 ppm of OH produced by electrical melting of natural quartz powder were measured using an interferometric dilatometer in the temperature range 300–970 K. The data obtained show several maxima and minima, some of which correspond to the phase transitions in crystalline silica. A sharp maximum is observed at 500 K, which corresponds to the &agr; to &bgr; transition temperature of cristobalite. Minima at 850 and 580 K correspond to low- to high-temperature phase transitions of crystalline quartz and tridymite, respectively. This correspondence was not observed in synthetic fused silica containing about 800 ppm of OH. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366279

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Using a classical photocapacitance technique, we have transformed the well-known EL2 defects, related to the As antisite in GaAs, into their metastable states. Using the capacitance, we have monitored the temperature dependence of the electron occupancy of these metastable states at thermal equilibrium. From this study, we deduce that a level located at 40 meV below the conduction band is associated with electron ionization from the metastable EL2 states. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365724

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate that the ability of GaN-based light-emitting diodes to emit in the short-wavelength regime makes possible “hybrid” organic–inorganic semiconductor light-emitting diodes that consist of two parts: a GaN-based electroluminescent part and an organic thin-film-based fluorescent part that absorbs the electroluminescence and fluoresces at a longer wavelength resulting in color conversion. We also show that organic films with much improved surface smoothness may be obtained by deposition at reduced temperatures. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365725

出版商:AIP    

年代:1997

数据来源: AIP