摘要:

The ability to modify the stacking sequence of ultrathin films offers a unique way to change either the interaction strength or the doping, but demands a careful control of each atomic monolayer. Progress is hampered by the lack of a direct method that allows differentiation on a local scale between the various terminating layers of a crystal. Here, the combination of a vacuum annealing process and friction force microscopy reveals this local distinction on aSrTiO3surface. Using the friction contrast, we find how the terminating layer of a single crystal profoundly influences the terrace edge structure. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121155

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The optical and electrical characteristics of spray pyrolysis deposited aluminum oxide films are reported. The films were deposited from a spraying solution of aluminum acetylacetonate inN,N-dimethylformamide using an ultrasonic mist generator on (100) Si substrates. The addition of water mist during the spraying deposition process resulted in an overall improvement of the films characteristics. The substrate temperature during deposition was in the 450–650 °C range. Deposition rates up to 90 Å/s were obtained depending on the spraying solution concentration and substrate temperature with an activation energy of the order of 31 kJ/mol. The optical energy band gap for these films was 5.63 eV and the refractive index at 630 nm up to 1.66 was measured by ellipsometry. The electrical characteristics of the films were determined from the capacitance and current versus voltage measurements of metal–oxide–semiconductor (MOS) structures incorporating them. A dielectric constant of 7.9, interface states density of the order of1011×1/eV cm2as well as breakdown fields higher than 5 MV/cm were determined in this way. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121156

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Several vibrational bands were observed near3100 cm−1in GaN that had been implanted with hydrogen at room temperature and subsequently annealed. Our results indicate that these bands are due to nitrogen-dangling-bond defects created by the implantation that are decorated by hydrogen. The frequencies are close to those predicted recently forVGa–Hncomplexes, leading us to tentatively assign the new lines toVGadefects decorated with different numbers of H atoms. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121157

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Correlation between chemical bonds, energy bands, and the corresponding properties of oxides and nitrides is established. It is proposed that an oxygen or nitrogen atom can hybridize and form a tetrahedron with its four neighbors through bonding orbitals and nonbonding lone pairs. As a result, the energy states of the host material are modified with four additional features, namely,sp3-hybrid bonding, nonbonding (lone pair), antibonding (dipole), and hole states. Therefore, oxygen and nitrogen possess the special ability of not only enlarging the band gap by hole production but also adding an antibonding subband above the Fermi level. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121158

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Boron segregation in an implanted arsenic profile in Si during annealing was investigated under various annealing conditions. It was found that both the implant damage created by arsenic implantation and arsenic deactivation enhance the diffusion of the embedded boron layer toward the shallow As implanted profile. The segregation phenomenon was observed in both 650 °C furnace annealed (FA) and 1000 °C rapid thermally annealed (RTA) samples. For the 650 °C FA sample, the boron segregation peak was located at the junction formed by implanted As, where residual dislocation loops at the original amorphous/crystalline (a/c) interface were also observed. However, noa/cinterface dislocation loops were found to be present for the RTA samples. Additional anomalous boron segregation was observed for the 1000 °CRTA+750 °C FAsamples. The additional boron segregation is not correlated with defect layers. It is, therefore, concluded that the anomalous boron segregation is caused by the electric field resulting from the formation of ap-njunction. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121159

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

In this letter, we present an atomic force microscopy study of a series of Te-mediated InAs/GaAs samples with InAs coverage ranging from 1.5 to 3 monolayers. We were able to directly identify the growth mode transition and the mechanism of relaxed island formation. At the limit of coherent growth mode, strained quantum dots aggregate, forming twin quantum dots (TQDs), which are structures of two, or more, dots virtually bonded together, separated by less than 3 nm. The onset of the incoherent mode is then unambiguously characterized by the coalescence of individual TQDs forming initially small, and then larger, relaxed islands. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121160

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

SiO2/Si(111)interfaces formed by a furnace oxidation are studied by a scanning reflection electron microscopy (SREM). SREM observation indicates that the initial atomic steps on a Si(111) surface are preserved at theSiO2/Siinterface and the interfacial steps do not move laterally even after 48-nm-thick oxidation. A profile analysis of reflection high-energy electron diffraction shows that theSiO2/Siinterface consists of islands which have a diameter of about 5 nm and monolayer depth. Our results indicate that the layer-by-layer oxidation caused by two-dimensional island nucleation proceeds under furnace oxidation. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121161

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A method of controlling threading dislocation densities in Ge on Si involving graded SiGe layers and chemical-mechanical polishing (CMP) is presented. This method has allowed us to grow a relaxed graded buffer to 100&percent; Ge without the increase in threading dislocation density normally observed in thick graded structures. This sample has been characterized by transmission electron microscopy, etch-pit density, atomic force microscopy, Nomarski optical microscopy, and triple-axis x-ray diffraction. Compared to other relaxed graded buffers in which CMP was not implemented, this sample exhibits improvements in threading dislocation density and surface roughness. We have also made process modifications in order to eliminate particles due to gas-phase nucleation and cracks due to thermal mismatch strain. We have achieved relaxed Ge on Si with a threading dislocation density of2.1×106 cm−2,and we expect that further process refinements will lead to lower threading dislocation densities on the order of bulk Ge substrates. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121162

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The impact of a deuterium(D2)sinter under two different annealing conditions, 450 °C/60 min and 450 °C/90 min, was studied and compared to the traditional forming gas (FG) sinter. Channel hot carrier (CHC) measurements indicated that while theD2sinter for 60 min improves the lifetime of the devices by10×over the FG sinter, an additional increase in theD2anneal time actually has a negative impact on lifetime. DC current–voltage measurements also showed that samples sintered inD2ambient for 60 min were the least prone to degradation under stress. Gated diode results showed no appreciable amount of difference in the initial interface state density among the different samples. Secondary ion mass spectroscopy indicated that neither poly nor salicide appears to be a complete barrier toD2diffusion. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121163

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We investigate a new type of magnetoresistance (MR) in which the resistivity of a near-surface two-dimensional electron gas is controlled by the magnetization of a submicron ferromagnetic grating defined on the surface of the device. We observe an increase in resistance of up to∼1500&percent;at a temperature of 4 K and∼1&percent;at 300 K. The magnitude and temperature dependence of the MR are well accounted for by a semiclassical theory. Optimization of device parameters is expected to increase considerably the magnitude of the room temperature MR. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121164

出版商:AIP    

年代:1998

数据来源: AIP