摘要:

The annealing kinetics of extended defects inSi+-implanted Si have been investigated byin situannealing plan-view transmission electron microscopy (TEM) samples in a TEM. A ⟨100⟩ Czochralski-grown silicon wafer was implanted with 100 keVSi+at the subamorphizing dose of2×1014cm−2.Following implantation, the effect of annealing of 800&hthinsp;°C was studied byin situannealing. After 5 min of annealing at 800&hthinsp;°C, a dense collection of both {311} defects(3×1011/cm2)and small subthreshold dislocation loops(1×1011/cm2)were observed. Upon subsequent annealing, the {311} defect density decreased rapidly and the loop density increased. The evolution of approximately 500 {311} defects could be followed as a function of annealing time. The unfaulting of a {311} defect was observed to be the source of every subthreshold loop observed to from (about 150 loops in the monitored region). After the initial 5 min anneal at 800&hthinsp;°C, the probability of a {311} unfaulting into a loop was about 50&percent;. Based on these observations, it is concluded that unfaulting of the {311} defects is the source of the subthreshold dislocation loops in nonamorphized ion-implanted silicon. 70&percent; of the loops formed were determined to have a Burgers vector ofa/3⟨111⟩,while 30&percent; were perfect with a Burgers vector ofa/2⟨110⟩.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122882

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report on a nanomachined electromechanical resonator applied as a mechanically flexible tunneling contact. The resonator was machined out of a single-crystal silicon-on-insulator substrate and operates at room temperature with frequencies up to some 73 MHz, transferring electrons by mechanical motion. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122883

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The adsorption of nitrogen (N) radicals (nitridation) on InAs (001) surfaces has been studied by ultrahigh-vacuum scanning tunneling microscopy and x-ray photoelectronic spectroscopy. The nitridation proceeds as Langmuir adsorption. The N adsorption at350 °Cis faster than that at100 °C,but N adsorption rates at100 °Con InAs and GaAs are almost the same. These results are explained as follows: at350 °C,N radicals bond mainly with the topmost In atoms on an In-stabilized surface, and at100 °C,N radicals replace As atoms in the topmost layer on an As-stabilized surface, and subsequently bond with In atoms in the second layer. The amorphous100 °Cnitrided surface layer is found to have an insulating characteristic without surface states. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122884

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The successful growth of self-organized quantum dots (QDs) of CdTe on ZnTe (100) surface by molecular beam epitaxy is reported. Atomic force microscope measurements on the uncapped samples revealed the formation of CdTe QDs with typical dot diameters of20±2 nmand heights of2.7±0.3 nmat 3.5-ML-thick CdTe deposited. The intensity of photoluminescence (PL) from the capped QDs was higher than CdTe/ZnTe single quantum wells (SQWs) by a few orders of magnitude at 4.2 K, and exhibited a thermal quenching with an activation energy of 110 meV, which is about twice as large as those in SQWs. In time-resolved PL measurements, the decay time was almost independent of temperature below 20 K. This is interpreted as due to the zero-dimensional excitonic properties in QDs. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122885

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Spectrally resolved measurements of the responsivity of infrared photodiodes based on InAs/(GaIn)Sb superlattices (SL) were performed in applied magnetic fields. For the field oriented parallel to the growth axis, interband Landau transitions related to both the center and the edge of the SL Brillouin zone in the growth direction were observed, in accordance with the parity selection rules that are expected for the type II system under consideration. For the field oriented perpendicular to the growth axis, the interband Landau resonances are broadened and the widening of the band gap is smaller. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122886

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We found unidirectional nanocracks in unidirectionally twinned films ofYBa2Cu3O7−&dgr;onNdGaO3which are normal to the twin planes. In 70–250 nm thick films, transmission electron and atomic force microscopy show that these unidirectional nanocracks are found to be 1–2&mgr;mapart and have 2–4 nm width. Microbridges that cross these nanocracks behave as natural Josephson junctions. They show Shapiro steps under microwave irradiation and suppression of the critical currentIcin magnetic fields. A very large in-plane anisotropy of the resistivities andIcwas observed and this was correlated with the nanocracks orientation, length, and film thickness. The observed anisotropy ofIcnearTcis shown to be consistent with ad+iswave symmetry of the order parameter inYBa2Cu3O7−&dgr;.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122887

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A micromagnetic study on antidot permalloy arrays is carried out in order to delimit their possibilities for high density storage. The dependence of the recorded bit quality on antidot size, separation distance, and film thickness is reported as well as hysteresis loops and coercivities. The simulations show a limit for the antidot size around 80 nm leading to maximum areal storage densities of about10 Gbits/in2.The results are interpreted in terms of demagnetizing, anisotropy, and exchange energies’ balance. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122888

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Magnetoinduced effects in second harmonic (SH) generation are experimentally studied in theCoxCu1−xgranular films. Significant nonlinear magneto-optical Kerr effect (NOMOKE) is observed both in longitudinal and transverse configurations. The interference of the SH fields generated by the interface and bulk, nonmagnetic and magnetoinduced nonlinear polarizations is discussed as a mechanism of NOMOKE enhancement. The bulk nonmagnetic dipole quadratic susceptibility of Co nanocrystals stems from the lack of inversion symmetry in the Co granules. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122889

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Cr doping inPr0.5Ca0.5MnO3is known to destroy the low-temperature antiferromagnetic charge-ordered state and to induce a ferromagnetic component as well as colossal magnetoresistance properties. Effects of Cr doping on the magnetic and nuclear structures are studied here by neutron diffraction forPr0.5Ca0.5Mn0.95Cr0.05O3.It is shown that, at low temperature, the strongly distorted charge ordered structure usually observed inPr0.5Ca0.5MnO3is replaced by a ferromagnetic phase in which the basal-plane distortion of theMnO6octahedra has disappeared, in agreement with the restoration of the double–exchange interactions. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122890

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have monitored the progression of the dewetting of a partially brominated polystyrene (PBrS) thin film on top of a polystyrene (PS) thin film with scanning transmission x-ray microscopy (STXM) as well as photoemission electron microscopy (PEEM). We mapped the projected thickness of each constituent polymer species and the total thickness of the film with STXM, while we determined the surface composition with PEEM. Our data show that the PBrS top layer becomes encapsulated during the later stages of dewetting and that atomic force microscopy topographs cannot be utilized to determine the contact angle between PBrS and PS. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122891

出版商:AIP    

年代:1998

数据来源: AIP