Resistance fluctations in submicrometer narrow Si inversion layers are studied over a wide range of temperatures and electron concentrations. Thermally activated switching on and off of discrete resistance increments is observed, caused by the capture and emission of individual electrons at strategically located scatterers (interface traps). The traps have a broad distribution of activation energies, as assumed in accounting for 1/f noise in larger devices.

We have measured the distribution in current for the onset of voltage in small-area Josephson junctions for temperatures down to ~1.6 K. The lifetime of the (V) = 0 state for our highest current density junctions becomes temperature independent for k B T %H(j)i/20 t SLT much less than the WKB prediction (co 0 is the junction resonant frequency). This is consistent with the Caldeira-Leggett theory, which includes damping effects on the quantum tunneling rate. PACS numbers: 74.50.+r, 05.04,+j, 72.70.+m Many experiments have studied the ramifications of the classical Langevin equation, but few have probed the low-temperature, high-frequency regime where quantum corrections to the picture must be expected. High-current-density Josephson tunnel junctions 1 at temperatures of a few kelvins make possible experimental studies 2 in this regime. Biased in the {V) = 0 state at currents near the critical current, the junctions are sensitive to fluctuations in the terahertz range, centered about their natural frequency, a> 0 . Fluctuation effects may be observed by sweeping the junction current through the critical current and noting the distribution, P{i), of current values at which voltage sets in. 3 P(i) should depend on whether k B T»Hu 0 /2 (classical regime) or k B T «h(x) Q /2 (quantum regime). 4 " 6 We have measured the width, a, of P(i) for junctions in the quantum regime and found that quantum effects do not appear until k B T)) = 2yMk B T.Without fluctuations, the phase can be trapped in a local minimum at cp^sin^x if x/[(1 -x 2 ) l/2 -x cos~lx]. No dc voltage develops across the junctions since {d

l the potential wells vanish and the phase increases at a speed determined by the damping and the overall steepness of the potential. This corresponds to the finite voltage state of the junction. We are interested in x slightly less than 1, in the presence of fluctuations. The phase is now restrained by a low barrier (inset, Fig. 1) which, in the absence of fluctuations, would hold ( V) = 0 until i exceeds i c . Fluctuations, however, cause p...

Piezoelectric thin film AlN has great potential for on-chip devices such as thin-film resonator (TFR)-based bandpass filters. The AlN electromechanical coupling constant, K(2), is an important material parameter that determines the maximum possible bandwidth for bandpass filters. Using a previously published extraction technique, the bulk c-axis electromechanical coupling constant was measured as a function of the AlN X-ray diffraction rocking curve [full width at half maximum (FWHM)]. For FWHM values of less than approximately 4 degrees , K (2) saturates at approximately 6.5%, equivalent to the value for epitaxial AlN. For FWHM values >4 degrees , K(2) gradually decreases to approximately 2.5% at a FWHM of 7.5 degrees . These results indicate that the maximum possible bandwidth for TFR-based bandpass filters using polycrystalline AlN is approximately 80 MHz and that, for 60-MHz bandwidth PCS applications, an AlN film quality of >5.5 degrees FWHM is required.

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present case, the ionization energy of the Hg 6s 2 valence electrons is 1.4 eV higher than that of the Cd 5s 2 . It should further be noted that the work in the early 1960's showed 2 that both the decrease of E g to zero and the high electron mobilities are associated with the metal s states of the conduction band decreasing in energy with increasing Hg content until they mix with thep states to form the valence-band maximum. We thus identify three phenomena (the breakdown of VCA, E g going to zero, and high electron mobility) as resulting from the Hg 6s 2 atomic levels being significantly below the Cd 5s 2 levels.Hg^^Cd^Te is perhaps the most promising material available for photodetection throughout the infrared, yet it has not been widely exploited. This may be because of difficulties in growing and handling the material 2 ; we suggest that this also results from the "s shift" (i.e., selectivity increasing the bonding energy of the Hg valence s levels, which weakens the Hg-Te bond and leads to the difficulties mentioned above).It is our hope that this paper will stimulate work to test our suggestions. Such work is greatly needed, both for fundamental understanding and to guide (and reduce the cost of) practical work.The conductance of narrow (0.1-jum) silicon inversion layers has been measured at low temperatures. A divergent, nonmetallic decrease of conductance is observed below 30 K, in excellent quantitative agreement with the combined theories of weak localization and interaction effects in their one-dimensional form, if one assumes parameters comparable to those observed in wide (two-dimensional) inversion layers. In this novel experimental system both localization and interaction effects are present and comparable in size.