摘要:

As shown by both its history and its present scientific and technological roles, hydrogen presents not only opportunities but distinct challenges. The opportunities, which once included aeronautics, now encompass semiconductors and electronics/opto‐electronics in general. Transportation has returned along with the grand prospect of a “hydrogen economy” based on more recent advances in the technologies of H generation and use. Challenges presented by H have grown acute for accelerator builders, especially in the areas of superconducting accelerating structures, large vacuum systems, and cryogenic systems. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1597351

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Hydrogen (H) is a most common element in biological molecules in general. Dihydrogen gas (H2) is both produced and consumed in many microorganisms. However, evolution has developed efficient systems preventing “the loss” of H2from biological ecosystems. Protons (H+) are often produced and used in biological systems to create proton (pH) gradients across biological membranes — a common mechanism generating ATP through the function of a specific ATP synthase, the universal biological energy carrier. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1597352

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Hydrogen has an important effect on the electrical properties of semiconductors and participates in a surprisingly rich variety of phenomena. This paper is an introductory survey of the properties of H and of H‐containing defects in semiconductors. A few technological applications and problems that involve H are also given. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1597353

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Hydrogen plays an important role as an impurity in solids. Hydrogen’s interactions with materials are discussed on the basis of its behavior as an isolated interstitial impurity. In most semiconductors and oxides hydrogen is amphoteric, always counteracting the prevailing conductivity of the material. But in some materials hydrogen acts as a source of conductivity. These concepts are illustrated with the example of hydrogen in zinc oxide. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1597354

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Hydrogen is a very common impurity which plays many roles hydrogen in crystalline Si. These are briefly reviewed. Several poorly understood issues are discussed, including the states of isolated interstitial hydrogen, the H‐enhanced diffusion of oxygen, and the formation of interstitial H2molecules. This paper concludes with preliminary results of ongoing research. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1597355

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Infrared (IR) and Raman spectroscopy are useful techniques for characterizing hydrogen‐related defects in semiconductors. This paper will focus on hydrogen in compound semiconductors such as AlSb, GaAs, GaN, InP, and ZnO. In most compound semiconductors studied to date, hydrogen forms neutral complexes with donors or acceptors. In GaN:Mg grown by metalorganic chemical vapor deposition, for example, hydrogen forms pairs with Mg acceptors so that the semiconductors is semi‐insulating as grown. In ZnO, however, theoretical and experimental work has shown that hydrogen is a shallow donor. We have observed hydrogen local vibrational modes in ZnO annealed in hydrogen gas, allowing us to speculate as to the structure of the hydrogen complex. The use of high pressures in conjunction with IR spectroscopy may provide a means for distinguishing between similar configurations. In GaN:Mg,H, the local vibrational mode exhibits a small shift with pressure. By comparing this shift with the predictions ofab initiocalculations, we can rule out the bond‐centered (BC) configuration. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1597356

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Muonium, formed by implanting positive muons into a semiconductor, provides a wealth of information on the analogous isolated hydrogen defect centers. Here we review the stable and metastable sites and motional properties for each charge‐state of Mu in the III‐V compounds, including the nitrides. The transitions among these states are described and generic energy diagrams are proposed for the zincblende and wurtzite structures to account for the observed dynamics. Finally, we discuss interactions with dopants in the muonium equivalent of hydrogen passivation. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1597357

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We have measured the frequency shift of the 817 cm−1bend mode ofH2*as a function of temperature by infrared absorption spectroscopy. The phase relaxation of the bend mode is dominated by low energy excitation of 270±9 cm−1modes. Further lifetime measurements by transient bleaching spectroscopy are necessary to elucidate the decay mechanism. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1597358

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Carefully controlled and calibrated experiments indicate a maximum capacity for adsorption of hydrogen on SWNTs is ∼8 wt&percent; under room temperature and pressure conditions. Samples displaying this maximum value were prepared by sonicating purified SWNTs in a dilute nitric acid solution with a high‐energy probe. The process cuts the SWNT into shorter segments and introduces a Ti‐6Al‐4V alloy due to the disintegration of the ultrasonic probe. The Ti‐6Al‐4V alloy is a well‐known metal hydride and its contribution to the measured hydrogen uptake was accounted for in order to assess the amount of hydrogen stored on the SWNT fraction. The principal purpose of this paper is to present key details associated with the measurement procedures in order to illustrate the degree of rigor with which the findings were obtained. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1597359

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Along with the technological challenges associated with developing fuel cells and hydrogen burning engines, a major issue that must be addressed to ensure the ultimate success of a hydrogen economy is the ability to store and transport hydrogen effectively. Millennium Cell has developed and patented a proprietary system for storing and generating hydrogen gas called Hydrogen on Demand™. The system releases the hydrogen stored in fuel solutions of sodium borohydride as needed through an easily controllable catalytic process. The fuel itself is water‐based, rich in hydrogen content, and non‐flammable. It can be stored in plastic containers under no pressure. After the hydrogen from the fuel is consumed, the remaining product, sodium metaborate (chemically similar to borax), can be recycled back into fresh fuel. In this paper, an overview of the Hydrogen on Demand™ technology is presented along with data showing the performance characteristics of practical hydrogen generation systems. A brief discussion of sodium borohydride regeneration chemistry is also provided. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1597360

出版商:AIP    

年代:1903

数据来源: AIP