ISSN:1057-9257    

DOI:10.1002/amo.860020102

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe pyrolytic LCVD of high‐purity gold tracks from the organogold(I) complex MeAuPMe3is reported. The tracks were deposited onto (100) n‐type single‐crystal silicon with a thermally grown oxide layer (3000 Å), single‐crystal GaAs with an intact native oxide layer and polycrystalline diamond films upon (100) silicon using the output from an argon ion laser (Coherent Innova 100‐10) at 514.5 nm. Deposits were grown at a range of scan speeds from 0 to 200 μm s−1and characterised by SEM, SIMS, LIMA and scanning profilometry. Electrical resistivities as low as 7.04 μΩ cm, within a factor of three of that of bulk gold, were achieved at scan speeds below 156.3 μm s−1. These are consistent with deposit purities of better than 99% (LIMA) without the need for a post‐deposition annealing step.The relationship between power density, beam residence time and deposition rate was measured. The morphology of the deposit from the onset of detectable nucleation through to the formation of continuous tracks was analysed by SEM micrographs of deposits grown at successively increasing power densities. The nucleation process was found to be substrate‐dependent. Changes in deposit morphology with power density and scan speed were observed. These include periodicity in track width and at high power densities the development of ‘volcano’‐shaped profiles.The formation of a phosphorus‐based interfacial layer, exclusive to laser deposition upon GaAs, is evidence for a rea

ISSN:1057-9257    

DOI:10.1002/amo.860020103

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe conventional thin film deposition equipment of LPVD has been modified for the preparation of nanometre‐layer stacks of uniform thickness at reduced target/substrate separation. Therefore the planar target was replaced by a cylindrical one and the target motion regime has been modified.During thin film deposition a substrate translation is preferred instead of the usual rotation technique. With this arrangement the emission characteristic of the plasma source can be computer controlled and tailored via a stepper‐motor‐driven manipulator for the desired layer thickness profile across an extended substrate. Thus, for example, a homogeneous film thickness is obtained even for lower target/substrate distances, and an appropriate deposition rate can be maintained.First applications of the equipment are explained and compared with typical results of the conventional tech

ISSN:1057-9257    

DOI:10.1002/amo.860020104

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractAtomic‐scale material‐processing tools must be developed to allow thein situsynthesis of complex, nanometre‐scale, multilayer structures. These processing tools must be cost‐effective, extendible to large‐area surfaces and adaptable to realistic manufacturing equipment. Presented here are experimental results on the photophysical processes in low‐fluence UV laser radiation of surfaces. The results suggest that atomic‐level synthesis/modification of materials is possible by the laser‐induced desorption by electronic excitation (LIDEE) process. The processing action employs resonance behaviour to gain species selectivity in the products desorbed. It naturally lends itself to automation (pulsed processing) and is designed for manufacturing laser systems currently used in materials processing. In addition, no potential limitations exist on the surface area which can be processed. Presented are the experimental data using crystalline Al and Bi2Sr2Ca1Cu2O8targets along with supporting results from Ag and W targets. The results are interpreted in the light of photodesorption models which best support the data. As a conclusion we present an outline of how the LIDEE process might be used as a nanometre‐scale materia

ISSN:1057-9257    

DOI:10.1002/amo.860020105

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the conventional high‐temperature thermal oxidation and rapid thermal oxidation processes used to fabricate commercial SiO2/Si structures at ∼850–1050°C, the SiO2/Si interface and the bulk oxide are formed at thesame time. We have developed a low‐temperature process for the formation of SiO2/Si structures at 200–300°C that separately controls and optimizes the properties of the SiO2/Si interface and the bulk SiO2. This has been accomplished byseparating interface formation by plasma‐associated oxidation from bulk oxide plasma‐assisted deposition. The oxidation step (i) removes residual C contamination from the Si surface, (ii) prevents N incorporation at the interface from the O atom source gas N2O and (iii) forms an oxide layer ∼0.6 nm thick and an SiO2/Si interface with a trap density,Dit≈(1–4) × 1010cm−2eV−1. This type of process has also been extended to the deposition of multilayer oxide

ISSN:1057-9257    

DOI:10.1002/amo.860020106

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractAluminium microstructures (dots or strips) have been photodeposited on GaAs substrates via the decomposition of a solid precursor, the 2:1 hydride adduct of Al, called trimethylamine alane (TMAA).The dissociation of TMAA, the vapour pressure of which can be varied between 0.4 and 1 mbar by dilution in hydrogen carrier gas, has been achieved via a pyrolytic process using a CW Ar+laser operating in the visible range (488–514 nm). This decomposition reaction occurs at laser powers higher than 0.3 W, i.e. at laser‐induced temperatures higher than 130°C, and leads to the formation of high‐purity aluminium strips as observed from Auger electron spectroscopy (AES) and energy‐dispersive X‐ray analysis (EDX) data. The deposition rates are in the range 50–1400 Å s−1. The minimum of line resistivity measured versus scanning speed and laser power is 6.5 μΩ cm.The photolytic decomposition of TMAA has been performed at room temperature within the laser spot area using a CW UV laser (intracavity frequency doubler emitting at 257 nm). The formation of aluminium clusters has been observed at very low deposition rates (20 Å s−1). However, these tiny clusters react quickly with oxygen and are transformed into alumina clusters.All these results have been tentatively explained on the basis of the surface reactivity of H2and TMAA regarding GaAs or Al, as obtained by other workers through surface science techniques a

ISSN:1057-9257    

DOI:10.1002/amo.860020107

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractPulsed‐laser‐induced removal of particles from surfaces is a new cleaning technique. This laser cleaning can be performed on dry surfaces as well as on wet surfaces with a micron‐thick liquid film during pulsed laser irradiation to provide enhanced removal efficiency. Using the latter technique, to be called ‘steam laser cleaning’ here, we are able to remove epoxy, alumina, silicon or gold particles with diameters in the range 0.1–10 μm from silicon and ot

ISSN:1057-9257    

DOI:10.1002/amo.860020108

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe STM tip shape was found to change when nanofabrication using a scanning tunnelling microscope (STM) was attempted by applying voltage pulses between the tip and the sample. This change, which is considered to be caused by the voltage pulses, was studied systematically to investigate the thermal contribution to nanofabrication using STM tips. The tips become easily damaged as the pulse amplitude and pulse width increase or the tunnelling gap decreases. Thermal reaction, including thermochemical reaction, is considered to play an important role in such nanofabrication.

ISSN:1057-9257    

DOI:10.1002/amo.860020109

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractPulsed laser deposition (PLD) of materials is a growing field with applications to many systems. With many materials, however, a major problem is particulate formation due to splashing of molten droplets or ablation of solid clusters from the target. For the case of II–VI semiconductors we have found that careful selection of the laser power density and appropriate mastering of the beam could reduce particulate formation to a negligible level even with the use of pressed targets. In this work we have deposited a number of II–VI semiconductors and their alloys, using XeCl and Nd:YAG lasers, from pressed and bulk targets onto various substrates in high vacuum. The ternaries of ZnTe and ZnSe as well as of ZnTe and CdTe were studied in detail. We determined the optimum growth temperatures and deposition rates for the growth of optical quality films. X‐ray diffraction, optical absorption, energy‐dispersive X‐ray analysis and Raman scattering were used to characterise these films or grain size and orientation, optical band gap and alloy effects on pho

ISSN:1057-9257    

DOI:10.1002/amo.860020110

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe machining of several materials such as polymers, metals and ceramics using excimer lasers (193, 248 and 308 nm) was investigated. By photoablation, micrometer resolution can be achieved for polymers if the wavelength and fluence are chosen properly. High‐definition processing of metals is complicated by the occurrence of surface melting. An interaction between the ablation plume and the walls of the laser‐drilled holes leads to hole widening in the case of polymers at high fluences. For small structures (<100 μm) all materials investigated show a size‐dependent ablation rate. This effect has to be taken into account if a precise ablation depth is required for a pattern with structures of different

ISSN:1057-9257    

DOI:10.1002/amo.860020111

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY