摘要:

The critical current densityJc(B,T) of epitaxial YBa2Cu3O7−x(YBCO) thin films on LaAlO3was measured under different applied magnetic fields (0–7 T) with the temperature ranging from 65 to 79 K. At 65 K, the zero‐field critical current density of the best film was 5.8×106A/cm2; even at magnetic fields up to 7 T,Jccould reach as high as 1×106A/cm2. Strong anisotropy was observed at 79 K. The anisotropy behavior diminished with the decrease of temperature. Experimental results showed thatJcwas proportional to (Tc−T)3/2; this was in accordance with the theoretical explanation by the Josephson junction model for granular superconductors.

ISSN:0021-8979    

DOI:10.1063/1.346784

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Observations on deep levels introduced in silicon by &agr;‐particle irradiation are reported. Low‐dopedn‐type samples are used and deep level transient spectroscopy is applied to detect the deep levels. Preliminary results provide evidence for some new defect states in addition to those previously reported. The study also reveals interesting metastability and room‐temperature transformation effects associated with some of the deep levels introduced.

ISSN:0021-8979    

DOI:10.1063/1.346752

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The existence of phosphorus in grain boundary will cause thecaxis of &agr;‐Co to orient along the film normal. Furthermore, it has been found that the phosphorous segregation in the boundary is controlled by the MnSO4concentration in the bath through its effect on chemical or electrochemical properties of complex ions in the bath.

ISSN:0021-8979    

DOI:10.1063/1.347182

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The losses associated with leakage through thin‐film superconductors with film thickness comparable to the skin depth in the normal state, and to the penetration depth in the superconducting state, are described. The method is used to describe the surface resistance of YBa2Cu3O7films deposited on various substrates.

ISSN:0021-8979    

DOI:10.1063/1.346753

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Glasses based on Bi2O3, CaO, SrO, and CuO were first prepared as precursors to polycrystalline superconducting ceramics based on these oxides. These glasses were found to be transparent in the infrared to 11 &mgr;m. The infrared cutoff is approximately 6.5 &mgr;m. The refractive indices are surprisingly high being about 2.9.

ISSN:0021-8979    

DOI:10.1063/1.346754

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Defect states induced by radio frequency air plasma etching process inn‐type bulk silicon have been studied. Deep level transient spectroscopy shows that a deep center with a small electron capture cross section &sgr;tn=1.3×10−20cm−3and an energy level at 0.41 eV below the conduction band was induced by plasma treatment of previously electron‐irradiated Si samples. The spectral dependence of optical cross sections for this defect level was measured by deep level optical spectroscopy, showing that the defect has a strong electron‐phonon coupling with a Franck–Condon shift of about 0.4 eV, and that the defect core is repulsive for electrons. The defect anneals out above 400 K, and is also slightly unstable at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.346755

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new type of opto‐optical modulation effect in nematic liquid crystals is experimentally observed. The transmitted intensity of a He‐Ne laser beam passing through a liquid crystal sample while applying a dc voltage is modulated by illuminating the sample with a xenon flash lamp pulse. The response time is fast, of the order of several milliseconds. The modulated state lasts for about 500 ms. A modulated intensity of light as large as ten times the unmodulated one is obtained. The physical origin of this effect is also discussed.

ISSN:0021-8979    

DOI:10.1063/1.346756

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The effects of hydrogenation on the low‐temperature (5 K) photoluminescence properties of GaAs grown on InP substrate by metalorganic chemical vapor deposition are investigated. An emission band at ∼1.4 eV originating from the GaAs/InP interfacial region shows a 30‐fold increase in intensity relative to the GaAs band‐edge emission after exposure to hydrogen plasma for 30 min at 250 °C. This improvement in intensity is attributed to hydrogen passivation of defects at the heterointerface caused by the large (≊4%) lattice mismatch between GaAs and InP. Annealing the hydrogenated sample at 350 °C nullifies the passivation effect. Further, the 1.4‐eV band shifts to higher energy on annealing the sample in the temperature range 150–450 °C with the hydrogenated sample exhibiting a larger shift than the untreated sample. It is suggested that the annealing‐induced peak shift arises due to modification of the interface and that it is greater in the hydrogenated sample compared to the untreated sample.

ISSN:0021-8979    

DOI:10.1063/1.346757

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A scanning tunneling microscope was used to modify the surface structure of highly oriented pyrolytic graphite in air. By superimposing 0.1‐&mgr;s pulses on the substrate bias, we consistently manufactured hole‐hill combinations (‘‘bits’’) of 2–3 nm. A 40‐nm L‐shaped structure was created. We describe the experiments and relevant results.

ISSN:0021-8979    

DOI:10.1063/1.346732

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The specific contact resistance (&rgr;c) of Ohmic contacts to HgTe/Hg0.4Cd0.6Te heterostructures has been measured using a transmission line model. The lowest measured values of &rgr;c(1.7×10−3 &OHgr; cm2) corresponded to the In/HgTe/Hg0.4Cd0.6Te and Sn/HgTe/Hg0.4Cd0.6Te systems; while within the range of the other metal contacts examined (Ag, Al, Au, Cr, Cu, Ni, Pt, and Ti), &rgr;cwas independent of HgTe/Hg0.4Cd0.6Te interface reactivity. Comparative measurements have also been made with metal junctions formed to Hg0.4Cd0.6Te and HgTe.

ISSN:0021-8979    

DOI:10.1063/1.346733

出版商:AIP    

年代:1990

数据来源: AIP