摘要:

Changes in the crystal structure ofPb(Zr, Ti)O3(PZT) on a Pt electrode caused by annealing in hydrogen-containing ambient have been studied using analytical transmission electron microscopy. A decrease in Pb composition and distortion in Ti–O coordination occur at the PZT/Pt interface. These findings indicate that preferential reduction of Pb and sequential diffusion of Pb from the PZT to the Pt electrode play an important role in the changes of the PZT crystal. Thus, changes in crystal structure due to annealing in a hydrogen-containing ambient can be avoided by using electrode materials that prevent Pb diffusion. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122333

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A method for lowering the processing temperature ofPbZr1−xTixO3(PZT) films was developed utilizing a laser-assisted two-step process. In the first step, perovskite phase was initiated in the PZT films to a furnace anneal at low temperatures in the range of 470–550 °C, depending on the Zr/Ti ratio. Later, the films were laser annealed (using KrF excimer laser) at room temperature to grow the perovskite phase, and to improve microstructure and ferroelectric properties. It was found that this two-step process was very effective in producing excellent quality ferroelectric PZT films at low temperatures. It should be noted that although laser annealing of amorphous and/or pyrochlore films directly (one-step process) produced perovskite phase, the ferroelectric properties of these films, irrespective of the composition, were rather unattractive. Some possible reasons for the ineffectiveness of the one-step process were discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122334

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Multiwall carbon nanotubes can be bent by changing the current density of the electron beam in a transmission electron microscope. The effect could be observed in a small fraction of nanotubes in the investigated samples. The bending can be varied continuously, is reversible, and highly reproducible. On removing the force which makes them bend, they relax to their originally straight shape without any damage, thus exhibiting spring-like behavior. Possible mechanisms for this effect are discussed. ©1998 American Institute of Physics.&hthinsp;

ISSN:0003-6951    

DOI:10.1063/1.122335

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Through a tight-binding rigid-band approach we show that changes in the relative stability of theC54,C49,andC40phases ofTiSi2,with electrons per atom ratio, are produced by the corresponding differences in the electronic density of states at the Fermi level. In particular, by increasing this ratio the stable phase evolves fromC49toC54,and then toC40.Our microscopic model provides a straightforward interpretation of very recent experimental findings concerning the sizeable variations in the transition temperature betweenC49andC54TiSi2in the presence of Al or Mo layers. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122336

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The initial growth state ofCaF2/Si(111)has been investigated in the high-temperature regime(700 °C).At these growth temperatures the interface betweenCaF2and Si consists of CaF with the Ca atoms bound to the Si. Using friction force microscopy it is possible to distinguish between the interfacial CaF layer and the overgrowingCaF2with high lateral resolution: the CaF layer has a higher friction coefficient than the bulklikeCaF2.This material contrast has been used to investigate theCaF2nucleation on the interfacial CaF layer. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122337

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The redistribution of O and N during the final, thermal oxidation in dryO2step in the formation of ultrathin silicon oxide/nitride/oxide dielectric films (ONO) was investigated using isotopic tracing and depth profiling with nanometer resolution. The results show that the final oxidation step induces atomic transport of O and N species in the system, such that the formed ONO structures are not stacked layer structures, but rather a silicon oxynitride ultrathin film, having moderate concentrations of N in the near-surface and near-interface regions, and a high N concentration in the bulk. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122338

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The properties of ferroelectric films are known to degrade when subjected to hydrogen in forming gas anneals. Earlier studies have attributed this degradation to the loss of oxygen from these films during these anneals. In this study, we show that though oxygen is lost during forming gas annealing, hydrogen incorporation is the primary mechanism for the degradation of ferroelectric properties. Raman spectra obtained from the forming gas-annealed films show evidence of polar hydroxil[OH−]bonds in the films. The most probable site for hydrogen ions is discussed based on ionic radii, crystal structure, electrical properties, and Raman spectra. We propose that the hydrogen ion is bonded with one of the apical oxygen ions and prevents the Ti ion from switching. Pyroelectric measurements on forming gas-annealed capacitors confirm that the capacitors no longer possess spontaneous polarization. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122339

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A nanoscale-patterning method on silicon oxide using a self-assembled monolayer (SAM) was developed. The silicon surface with native oxide was additionally oxidized locally in dry nitrogen atmosphere by the field-induced oxidation (FIO) technique using an atomic force microscope with a conductive cantilever, and then immersed in octadecyltrichlorosilane (OTS) solution. The contact angle and topography image revealed that the OTS layer was formed only on the native oxide. In contrast, when FIO was performed under the humidity of 88&percent;, OTS SAM was formed on both FIO and native oxide. These results indicate that SAM formation on silicon oxides can be locally suppressed by FIO in a dry environment. By using this technique, we could fabricate a line structure of OTS SAM as narrow as 22 nm. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122340

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present a cross-sectional scanning tunneling microscopy (XSTM) study of the spontaneous ordering ofGa0.48In0.52PandGa0.52In0.48Pgrown on (001) GaAs substrates by molecular beam epitaxy (MBE) and organometallic vapor phase epitaxy (OMVPE), respectively. The (111)-type alloy ordering could be seen clearly in the OMVPE-grown alloy region. On the other hand, the MBE-grown region shows a very small degree of ordering as revealed by the STM. Most of the ordered region shows(InP)1(GaP)1-type ordering: alternating InP- and GaP-like(1¯11)planes. In addition to this type of ordering, we also observe another type of ordering consisting of two InP-like(1¯11)planes and one GaP-like(1¯11)plane that we call(InP)2(GaP)1-type ordering. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122341

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We fabricated laterally confined GaAs–AlGaAs superlattices with diameters between 500 nm and 2 &mgr;m. With decreasing device diameter, a gap evolves in the current–voltage curve around zero bias and steps show up at the onset of the current. This behavior is interpreted in terms of Coulomb blockade, a depletion of the center of the superlattice, and single-electron tunneling through donor levels. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122342

出版商:AIP    

年代:1998

数据来源: AIP