摘要:

The room‐temperature attenuation for longitudinal acoustic waves propagating in thecdirection in high‐purity CdS has been measured from 0.1 to 0.6 GHz. At 0.5 GHz the attenuation is 46 dB/cm (tan&dgr;=0.0015). From the observed attenuation corrected for phonon‐electron contributions and a lattice loss theory of Woodruff and Ehrenreich, a Gru¨neisen parameter of ± 1.51 is calculated. An alternate method of calculating the Gru¨neisen parameter by using the pressure dependence of the elastic constants gives a Gru¨neisen parameter of ‐1.37.

ISSN:0003-6951    

DOI:10.1063/1.1655131

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Single‐crystal films of aluminum nitride were fabricated on (0001)‐ and (011¯2)‐oriented sapphire substrates by reactive rf sputtering an aluminum target in ammonia gas. Films sputtered on either sapphire orientation were clear, smooth, and piezoelectric. Effective surface acoustic wave piezoelectric coupling constants as large ask2= 0.2% were found for films sputtered on (0001)‐oriented sapphire.

ISSN:0003-6951    

DOI:10.1063/1.1655132

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

An electron microscopic diffraction study for circular stacking faults in silicon has been carried out. For the first time it has been possible to make direct correlation between the faults and subsurface precipitates, and to confirm that circular fault growth involves climb of a Frank dislocation from a precipitate site.

ISSN:0003-6951    

DOI:10.1063/1.1655133

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Surface acoustic waves on quartz have been used for acousto‐optic deflection in Ta2O5waveguides. Deflection efficiencies for TM modes of up to 93% have been observed with an acoustic power of 175 mW.

ISSN:0003-6951    

DOI:10.1063/1.1655134

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

We report the observation of dc effects in elastic surface waves on 131° rotatedY‐cutX‐propagating LiNbO3. A simple model to account for these effects is suggested.

ISSN:0003-6951    

DOI:10.1063/1.1655135

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

This letter reports the development of a mechanically scanned acoustic microscope showing 10‐&mgr;m resolution. Using single‐surface lenses an acoustic beam is focused with negligible spherical aberration in a water cell. The image is formed by mechanically scanning an object through this focused beam in a raster pattern. Transmitted power is detected with a piezoelectric transducer, and this signal modulates the synchronized raster of a CRT display. By employing piezoelectric detection, sensitivities of 10−8W/cm2are obtained, yielding images of excellent clarity and contrast.

ISSN:0003-6951    

DOI:10.1063/1.1655136

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The fraction of electrical power converted into spurious bulk waves at a surface interdigital transducer operating on and near surface wave resonance was measured. Bulk wave generation ony‐zlithium niobate was found to be strong below, at, and above resonance and to increase with decreasing number of finger pairs.

ISSN:0003-6951    

DOI:10.1063/1.1655137

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Calculations are presented which indicate that the maximum theoretical solar conversion efficiency of Schottky‐barrier solar cells is very similar to that of conventional homojunction solar cells, e.g. values of 22–24% apply to Si, and ∼ 25% to semiconductors having a band gap between 1.4 and 1.6 eV.

ISSN:0003-6951    

DOI:10.1063/1.1655138

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Detailed calculations have been performed to show the importance of refractive effects on laser‐induced breakdown in gases. The refraction, which results from gradients in the density of plasma electrons, can cause a loss of energy from the beam and an apparent dependence of breakdown threshold on beam or focal spot size.

ISSN:0003-6951    

DOI:10.1063/1.1655139

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The pressure dependence of the threshold energy for CO2laser gas breakdown in helium and nitrogen has been measured in the pressure range 40–70 Torr. The striking difference in the pressure dependence for the two gases is a clear manifestation of the effect of inelastic energy losses upon the avalanche breakdown process. This difference can be predicted by simple physical arguments or by scaling results from dc gas breakdown experiments to CO2frequency.

ISSN:0003-6951    

DOI:10.1063/1.1655140

出版商:AIP    

年代:1974

数据来源: AIP