摘要:

X-ray and ultraviolet photoemission spectroscopy investigations reveal strong interactions between Ca and tris-(8-hydroxy quinoline) aluminum(Alq3)during theCa/Alq3interface formation. The details of the interaction depend on the direction of the interface formation. For the case of Ca deposited onAlq3,a staged interface reaction is observed. For low Ca coverages(&THgr;Ca⩽4 Å),negatively chargedAlq3radical anions are formed by electron transfer from the Ca. The emergence of new states in the energy gap is observed in the UPS spectra. At higher coverages, the Ca reacts with the phenoxide oxygen resulting in the decomposition of theAlq3molecule. On the other hand, for the case ofAlq3deposited on Ca, a strong chemical reaction takes place as soon asAlq3is deposited, and Ca attacks every constituent ofAlq3.Finally, no interaction occurs betweenAlq3and the Ca substrate if the substrate has been passivated by oxygen prior to theAlq3deposition. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121100

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Two different effective thresholds for the onset of nonlinearity in the dielectric and piezoelectric coefficients of donor-doped lead zirconate titanate (soft PZT) piezoceramics at electric ac fieldsEc1≈100 V/cmandEc2≈1 V/cmare found. Both are characterized by a scaling behaviorx=x0+A[E−Ec)/Ec]&fgr;above the respective threshold, wherexis the dielectric or piezoelectric coefficient. The values of the effective exponent &fgr; are apparently independent of the particular ceramic system which suggests a universal behavior in soft PZT. We suggest that the nonlinearity is dominated by the dynamics of domain walls in a randomly pinned medium. ©1998 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.121101

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Viscosity and enthalpy relaxation from the amorphous state into the supercooled liquid state was investigated in the bulk metallic glass formingZr46.75Ti8.25Cu7.5Ni10Be27.5alloy below the calorimetric glass transition. At different temperatures, the viscosities relax into states that obey the same Vogel–Fulcher–Tammann relation as the data obtained at higher temperatures in the supercooled liquid. Enthalpy recovery experiments after relaxation in the same temperature range show that the enthalpy of the material reaches values that also corresponds to the supercooled liquid state. The glass relaxes into a metastable supercooled liquid state, if it is observed on a long time scale. Equilibration is possible far below the calorimetric glass transition and very likely even below the isentropic temperature. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121102

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Manipulation of Ag nanocrystals derived from up to 200 000 atoms was performed using the tip of a scanning tunneling microscope. By varying the scanning conditions, it was possible to move them laterally on contamination-free Si(111)-7×7 surfaces or to remove them. In both cases, thin Ag tracks were left behind. This demonstrates the concepts of nano patterning and nano painting with metals on clean semiconductor surfaces. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121103

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A 10 Å ultraviolet/ozone grown oxide was used as an atomic diffusion barrier in a Ge/GaAs heterostructure. Good thermal stability of the oxide layer has been demonstrated by the appearance of dendritic crystallization [K. M. Lui, K. P. Chik, and J. B. Xu, J. Appl. Phys.81, 7757 (1997)], induced byin situthermal pulse annealing, of the Ge overlayer. In this work, an abrupt heterointerface was revealed by aligned Rutherford backscattering spectroscopy after annealing and compared with a control with no barrier at the interface where considerable diffusion had taken place. Current–voltage measurement indicated good rectifying properties of the oxide barrier heterojunction. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121104

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Thermal stability of fluorinated amorphous carbon (a-C:F) thin films with a low dielectric constant was investigated by electron spin resonance (ESR), infrared (IR) absorption, optical absorption, and x-ray photoelectron spectroscopy (XPS) as well as measurements of film thickness and dielectric constant. IR and XPS measurements suggested that the strength of theCF3andCF2bonding configurations against annealing are weaker than that of the CF bonding configuration. ESR measurements revealed that the dangling bond density decreased by one order of magnitude after annealing at 300 °C and increased after annealing at 400 °C. Furthermore, thegvalue and the linewidth of the ESR spectrum decreased with increasing annealing temperature. Based on these results, the changes in structure and defect configuration are discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121105

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

In this letter, the use of an ordered ultrathin ZnSe dipole layer to significantly modify the band discontinuity at the Si/Ge(111)-c(2×8)heterojunction is reported. Soft x-ray photoemission spectroscopy (SXPS) was utilized to monitor the evolution of the interface. The ZnSe intralayer increased the valence band offset by ∼0.57 eV, as compared to a negligible valence band offset for the Si/Ge(111) junction. This dramatic modification is interpreted in terms of the charge transfer at the interface. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121106

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

1.54 &mgr;m photoluminescence has been observed from GaN doped with Er during growth by metalorganic molecular beam epitaxy. StrongEr3+-related photoluminescence (PL) was measured at room temperature for GaN:Er doped during growth onc-planeAl2O3and Si. Experiments to evaluate the effects C and O on the optical activity of Er indicated that these impurities dramatically enhance Er PL in GaN. GaN films doped with Er to a concentration of3×1018 cm−3with[O]∼1020 cm−3and[C]∼1021 cm−3luminesce at 1.54 &mgr;m with an intensity ∼2 orders of magnitude greater than films with oxygen and carbon backgrounds of less than1019 cm−3.The thermal PL quenching behavior was also markedly different for samples of varying O and C content.Er3+luminescence from samples with high O and C concentrations quenched by only 10&percent; between 15 and 300 K while the integrated PL signal from the samples with lower [O] and [C] quenched ∼85&percent; over the same temperature range. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121107

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The gettering of implanted Pt and Ag to hydrogen-induced cavities in Si has been compared for doses from1×1013to1×1015 cm−2.After annealing at 850 °C for 1 h, almost 100&percent; of both implanted metals were relocated to the cavity band for doses less than1×1014 cm−2.At higher doses, large differences were observed in the gettering behaviour of Pt and Ag, where the amount of Pt was saturated at close to a monolayer coverage of cavity walls, whereas the Ag accumulation at cavities continually increased with dose. Cross-sectional transmission electron microscopy revealed strong differences in the ability of Pt and Ag to form a bulk phase at the cavities. The results indicate that stable silicide formation at the near-surface and trapping of Ag to implantation damage are the main processes which limit gettering at the higher doses. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121108

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

This letter describes the use of micromolding in capillaries in combination with screen printing to form organic microstructures for applications in microelectronics. Fabrication of plastic transistors with micron feature sizes demonstrates the approach. The performance of these transistors compares favorably with that of similar devices constructed using conventional methods and inorganic substrates, dielectrics, and conductors. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121109

出版商:AIP    

年代:1998

数据来源: AIP