摘要:

The two-dimensional electron gas in &dgr;-doped double quantum wells has been studied by using the Shubnikov–de Haas measurement. It was discovered that the &dgr;-doping layer at the central barrier is able to prevent the electron coupling in the two wells and that the persistent photoconductivity can be reduced due to the thinner barrier. A &dgr;-doped multiple quantum well structure for photodetector application was also proposed. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365372

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An intrinsic characteristic of the “colossal” magnetoresistance manganite compounds is that the resistance and the magnetoresistance vary strongly with temperature over the small temperature regime in which the magnetoresistance is exceptionally large. We propose a heterostructure constructed of layers of varying composition manganites which extends the regime of large magnetoresistance and greatly broadens the sharp peak in resistance. Data from a prototype heterostructure are presented that demonstrate the effectiveness of this method. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365373

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Metal based single electron transistors are fabricated by the step edge cut off process. Titanium metal lines with a width of 0.1&mgr;m are deposited on prepatterned silicon substrates, that serve as the dielectric barriers for the tunnel junctions. In structures with multiple tunnel junctions, clear Coulomb blockade and Coulomb oscillation features can be observed at temperatures up to 77 K. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365374

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In a recent article [J. Appl. Phys.80, 1678 (1996)] Aksenov &etal; reported on electron paramagnetic resonance (EPR) studies in&bgr;-FeSi2crystals grown by chemical vapor transport. They did not perform a rigorous measurement of the angular variation of the EPR line positions. Consequently, there has been a drastic loss of information and most of their conclusions turn out to be erroneous. It is shown that the anisotropic signals(Ai,Bi)do not arise from spin triplet states but from centers withS=1/2 and their origins are notNi2+ions butNi+(Ai)andCr−(Bi)ions substituting for Fe on one of its two inequivalent lattice sites. The analysis of the line structure of the isotropic signal(C)is incorrect and hence, the structure cannot be attributed to a ligand hyperfine interaction with four iron atoms. Finally, the determination of an acceptor activation energy from the temperature dependence of theCsignal is not justified since no correction for the EPR intensity dependence due to the thermal population difference of the Zeeman levels was included. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365375

出版商:AIP    

年代:1997

数据来源: AIP