Experiments are reported which show that temperature gradients perpendicular to the surface of epitaxial normal conducting YBa2Cu3O7−δ films give rise to large transversal voltages between contacts on the film surface. The temperature gradients have been produced by pulsed laser irradiation and by continuous heating of the films by heater wires. To explain the large lateral voltages, an atomic layer thermopile is proposed, which may be formed by the layered structure of the material.
We report on the development of a low-cost, thin-film electrodeposited cadmium telluride solar cell. The most efficient cell developed to date had an efficiency of 8.6% (under AM1 illumination), an open circuit voltage of 0.723 V, a short circuit current density of 18.7 mA/cm2, and a fill factor of 0.64. The cell uses a Schottky barrier rectifying junction at the front surface and a cadmium ohmic contact at the back. Passivation of the top surface improves the photovoltaic properties of the rectifying junction.
and ZnTe substrates at35o'C with atmospheric pressure MOVPE. DiisoproWItelluride, dimethylzinc-triethylamine and diethylzinc were chosen as metallorganic precursors. The samples were characterized by photoluminescence at 2 K and the Hall effect. In the R spectra the light hole, heavy hole and bound exciton transitions are well resolved. Most of the transitions have been assigned. The partial pressure ratios of the alkyls were optimized. The influence of composition and stoichiometry of the substrates on the purity of the ZnTe is revealed. Various alkyls as sources of As, Bi, Ga. In and I were investigated for their suitability as p-or n-type dopants. It is shown that telraethylbiarsine and ethyliodide are promising alkyls for p-and n-type doping of ZnTe. Zinc telluride layers have been grown on (100) GaAs, GaSb I 54 671 @U Bumn 49 452 (in Japanese) Len. 14 151 Stare Commwa 2 157 Saminadayar K 1985J. Cyst. Gmwth 7.2 194 E p z q (London: Acadimic) " d e l R.
The optical response of granular Tl-Ba-Ca-Cu-0 films has been used to investigate thermal properties of the films. An analysis of the response using a heat transfer model yields a thermal diffusivity D= 10m3 cm*/s at 150 K which rises to 6 x lo-' cm'/s at a temperature of 30 K and allows for an estimation of the boundary resistance Rbdz lop3 K cm*/W between film and substrate. The dependence of the response time on film thickness obtained from the heat transfer model is compared with published data indicating that in many experiments the observed response is mainly bolometric in origin.Since it has become possible to prepare high T, superconducting films, much attention has been focused on their optical response, where films are irradiated with pulsed radiation (visible to far infrared) and the transient resistance change of the films is measured. Response times on a remarkably large time scale between milliseconds and picoseconds have been found meanwhile, and were attributed to a variety of different physical mechanisms.1-14 Irradiation induced heat production within the films leads to a bolometric response due to the temperature dependent film resistance. In this case the response time is governed by film cooling due to heat diffusion into the substrate. It is the purpose of this letter to demonstrate, that an analysis of the resistance response of a Tl-Ba-Ca-Cu-0 film can be used to investigate the thermal diffusivity of the film as well as the thermal boundary resistance of the film-substrate interface. Furthermore, a comparison of published data with response times obtained from the heat transfer model allows a clear separation of bolometric and nonbolometric responses.The measurements were carried out on polycrystalline Tl-Ba-Ca-Cu-0 films grown on MgO substrates by a laser ablation technique. l5 The films were patterned by means of an excimer laser into 200~pm-wide stripes with contact pads on both ends. Thin copper wires were attached using silver epoxy paint and the stripes were biased using a constant current source (see the inset of Fig. 2). The samples were mounted in a temperature variable optical cryostat and irradiated with short pulses from an atmospheric pressure CO? laser (pulse duration zz 80 ns, wavelength z 10 pd.The dependence of the resistance R on temperature T of a tilm of 1 ,um thickness is shown in Fig. 1 for several bias currents. A suthciently high current leads to nonzero dR/dT even at low temperatures, allowing measurements of the bolometric signal well below T,. Response measurements at two temperatures are shown in Fig. 2 for this film. With a laser pulse energy density z-3 mJ/cm* the maximum resistance change was several ohms at 120 K indicating an overall temperature change of the film of the order of 5 K. At 50 K, due to the smaller value of dR/dT, the resistance change was 0.5 Sz. Comparison of the measurements clearly shows a shorter resistance recovery time at low temperature due to faster heat diffusion.By use of a heat transfer model thermal properties of the high T, mat...
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