摘要:

Single crystal 3C-SiC epitaxial films are grown on Si(111) surfaces using tetramethylsilane by rapid thermal chemical vapor deposition. Strong blue/green photoluminescence (PL) was observed at room temperature from the free films of SiC prepared by etching the Si substrate. The main PL peak energy varies from 2.1 to 2.4 eV with full widths at half-maximum between 450 and 500 meV, depending on the growth condition, excitation wavelength and excitation light intensity. A weak peak at 3.0 eV also appeared. The infrared (IR) spectra of free films of SiC exhibit modes associated with CH and OH groups. We also compared PL characteristics of free films of SiC with those from porous SiC produced by anodization of SiC/Si to determine the origin of the PL. Porous SiC shows a PL peak centered at 1.9 eV, different from those in SiC. From the analysis of the IR spectra and scanning electron microscopic images, we tentatively suggest that the origin of the PL from free films of SiC might be associated with an OH group adsorbed on defects or some localized states as is the case for an amorphous SixC1−xalloy. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118648

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Stacked series arrays of intrinsic Josephson (IJ) tunnel junctions have been fabricated on the surfaces ofBi2Sr2CaCu2O8+&dgr; single crystals using photolithography and Ar-ion milling together within situmonitoring of the resulting current–voltage(I–V)characteristics. The number of unit-cell-sized junctions in the stack (along thec-axis) may be varied from 1–5 to∼200 in a controlled way. Thec-axis resistivity&rgr;c,estimated from the resistance of an individual tunnel junction is ≈30 &OHgr; cm at 90 K. The temperature dependence&rgr;c(T)∝ exp(&Lgr;/T)with&Lgr;≈43meV, suggesting thermally activated hopping mechanism of transport in thec-axis direction. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119079

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

c-axis texturedLa0.7Sr0.3MnO3−&dgr;(LSMO) films were fabricated onSiO2/Si(001) substrates using aBi4Ti3O12(BTO) template layer. Electrical and magnetic properties of LSMO were investigated. The LSMO/BTO layer of this structure has no in-plane alignment. Even though a ferromagnetic transition temperature,TC,is as high as that of the epitaxial LSMO film (360 K), a resistivity peak temperature,TP,is about 140 K lower thanTC.The resistivity behavior as a function of temperature for LSMO/BTO/SiO2/Si films is found to be dominated by grain boundary effects. Low field sensitive magnetoresistance which suggests spin tunneling through the grain boundaries is also observed at room temperature. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118649

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Strongly textured NiFe(111) underlayers, deposited by dc magnetron sputtering with applied substrate bias, are utilized to grow large, epitaxial grains of FeMn(111). These perfectly oriented (111) NiFe/FeMn bilayers exhibit the highest interfacial exchange anisotropy energy(0.17 erg/cm2),lowest coercivity (∼2 Oe) of the pinned layer, and highest blocking temperature (205 °C) ever reported, to the best of our knowledge. The relationship between the blocking temperature and the x-ray diffraction intensity of FeMn(111) indicates that the exchange interaction across the NiFe and FeMn interface is enhanced by the well-oriented, large, defect-free FeMn(111) crystals. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118650

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report spin-dependent perpendicular transport in the magnetic trilayer junction structureLa0.67Sr0.33MnO3/SrTiO3/La0.67Sr0.33MnO3.Large (factor of 5) changes of magnetoresistance induced by a field of∼200Oe are observed at4.2K. JunctionI–Vcharacteristics at low temperatures are consistent with a metal–insulator–metal tunneling process with a large spin-polarization factor of0.81for the conduction electrons. Above100K, a variable range-hopping conduction shunts out the magnetoresistance contribution. This second conduction channel comes from the impurity states within SrTiO3barrier and therefore is not an intrinsic limit to the magnetoresistance performance of the device at high temperatures. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118651

出版商:AIP    

年代:1997

数据来源: AIP