摘要:

We calculate the eigenfrequencies of a rectangular cantilever of an atomic force microscope immersed in a fluid or a gas. To do so, the problem of combined elastomechanical and hydrodynamical equations is solved approximatively. The results are compared with experimentally obtained frequencies. For water the difference between experiment and theory is less than 4&percent; if the ratio of the height of the cantilever to the width is less than1/20and if the corresponding eigenmode has at least four nodes. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365379

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Observation of enhanced negative-ion formation in ArF–excimer–laser irradiated silane was reported in a recent paper [L. A. Pinnaduwage, M. Z. Martin, and L. G. Christophorou, Appl. Phys. Lett.65, 2571 (1994)]. In that paper, preliminary evidence was presented to show that highly excited electronic states of silane or its photofragments could be responsible for the observed enhanced negative-ion formation. In the present paper, we report evidence, obtained using a new experimental technique, that the electron attaching species are high-Rydberg (HR) states of silane indirectly populated via laser irradiation and show that an absolute lower bound for the corresponding electron attachment rate constant is∼4×10−7 cm3 s−1.The initial capture of the electron by the HR states is likely to be a diabatic process and the large polarizabilities associated with the HR states appear to be responsible for the observed large electron attachment rate constants. We also measured electron attachment to thermally excited vibrational states of the ground electronic state of silane, which showed no measurable electron attachment up to 750 K. Implications of these observations in modeling of silane discharges used for plasma processing of amorphous silicon are discussed. It is also pointed out that large negative ion formation observed in many “weakly electronegative” plasma processing gas discharges could be due to enhanced electron attachment to HR states: such states could be populated via direct electron impact and/or via excitation transfer from the metastable states of rare gases that are commonly used in these processing discharges. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365381

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Experiments with nonlinear self-refraction of Gaussian laser beams in silica sono-gels doped with copper tetrasulfonated phthalocyanine are reported. The propagation of laser beams inside nonlinear sol-gel samples with different Cu-phthalocyanine concentrations has been monitored by measuring the spatial beam profile in the near field and in the far field behind the sample. The experimental results are analyzed by a new simple theoretical approach, in which we assume that the incident Gaussian beam induces a phase shift that varies as a Gaussian function of the beam radius. The beam propagation behind the sample is determined by the Huygens–Fresnel integral formalism. By solving the Huygens–Fresnel integral, analytical expressions for the spatial beam profile in both the near field and the far field after the nonlinear sample are obtained. Experiments are carried out with a diode pumped frequency doubled Nd–YAG laser at 532 nm. We obtain very large third-order nonlinearities in these doped sol-gel samples at temperatures just above room temperature. When we compare the predictions of the theory with the experimental data, we find experimental values of the nonlinear third-order susceptibility up to−2.3×10−4esu. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365551

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The energy, velocity, angle distribution of ions in magnetoactive electron cyclotron resonance plasma have been studied with a two-dimension hybrid mode. The dependence of these distribution functions versus position and pressure are discussed. Our simulation results are in good agreement with many experimental measurements. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365382

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The elastic and optical properties of organically modified silicates prepared by ultrasonics aided polycondensation of tetraethoxysilane and polidimethylsiloxane are studied by means of high resolution Brillouin spectroscopy. Nuclear magnetic resonance data evidence the microseparation of the organic and inorganic phases for the systems with high content of polymer formation. The elastic and optical properties are clearly influenced by the change in microstructure. We propose a three component mechanical model that qualitatively explains the observed variation of the elastic constantc11versus molar fraction of dimethylsiloxane in these vitreous materials and develop a structural model that accounts for the observed dynamical behavior. ©1997 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.365383

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The use of Cu in ultralarge scale integrated (ULSI) conductors has resulted in the need to prevent Cu diffusion. We evaluated the passivation effect of plasma-enhanced chemical-vapor-deposited silicon nitride (PECVD-SiN) using secondary ion mass spectrometry and atomic absorption spectrometry. From these measurements, it was found that a large amount of Cu diffused through PECVD-SiN films during the heat treatments of the metallization process, probably due to the rapid diffusion paths along the microdefects of PECVD-SiN films. However, Cu contamination was barely detected in the current–voltage measurements and bias-temperature stressing tests ofCu/PECVD-SiN/SiO2/Sicapacitors because the leakage current through SiN films slightly increased as a result of Cu diffusion. This result is attributed to the electric-field relaxation caused by a large number of electrons trapped in the PECVD-SiN films, of which the negative charge compensates the positive charge of Cu ions. Although the degradation of electrical characteristics is not explicitly observed in simulation usingCu/PECVD-SiN/SiO2/Sicapacitors, Cu atoms reach Si devices in the actual process. Therefore, the passivation effect of PECVD-SiN films is insufficient to allow application to ULSI devices. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365380

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The impression test of a Newtonian fluid under a constant load and for a small Reynolds number flow was simulated by using the finite element method. It is found that the penetration velocity is a constant if the surface tension/viscosity ratio is less than 0.1 cm/s, the product of surface tension and indenter radius is less than 0.05 of the applied load, and the penetration depth is less than1/3of the indenter radius. Such constant penetration velocity is proportional to the applied load and inversely proportional to the viscosity and the indenter radius. The stick or slip boundary condition at the interface between the indenter and the fluid has no effect on the penetration velocity under these conditions. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365384

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Phase transformation of amorphous-germanium thin film has been carried out on amorphous substrate byin situthermal-pulse annealing in a high vacuum chamber directly after evaporation. The microstructure of the resultant film was shown to depend markedly both on the annealing ambient and on the time of exposure(te)for the as-deposited films under full-powered(<102 W/cm2)incoherent broadband irradiation. The heating rate was estimated to be not less than102 K/s.The surface morphology of the sample was examined by atomic force microscopy (AFM), scanning electron microscopy, and optical microscopy. For samples annealed in air, hillock growth mode was observed, while for samples annealed in vacuum, a transition from the microgranular to dendritic grain growth, depending sensitively onte,was clearly evident. Surprisingly, the length of the crystallized dendrites could be as long as≃104 &mgr;m,being at least≃104times larger than the thickness of the film. The dendritic morphology, the implied growth rate, and the condition of crystallization lead us to suggest that the Ge film may exist in a supercooled semiconductive liquid phase just before crystallization. X-ray diffraction analysis revealed that grains were crystallized dominantly with a random orientation forte<2.84±0.05 s,while a sharp transition to a preferred ⟨110⟩ crystal orientation occurred at the criticalteof3.22±0.05 s,corresponding to a maximum temperature(Tm)of 577 °C reached by the system. This transition is consistent with the appearance of dendrites in AFM micrographs. More interestingly, an anomalous lateral size effect of the substrate on the misalignment of the ⟨110⟩ crystal direction of different grains with respect to the substrate normal was observed from the x-ray rocking curves. Careful inspection of the AFM images found that the giant dendrites broke up into individual columnar grains as the substrate width went down in size. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365385

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Aluminum doped zinc oxide (AZO) films are prepared by rf magnetron sputtering on glass or Si substrates using specifically designed ZnO targets containing different amount ofAl2O3powder as the Al doping source. The structural, electrical, and optical properties of the AZO films are investigated in terms of the preparation conditions, such as theAl2O3content in the target, rf power, substrate temperature and working pressure. The crystal structure of the AZO films is hexagonal wurtzite. The orientation, regardless of the Al content, is along thecaxis perpendicular to the substrate. The doping concentration in the film is 1.9 at. &percent; for 1 wt &percent;Al2O3target, 4.0 at. &percent; for 3 wt &percent;Al2O3target, and 6.2 at. &percent; for 5 wt &percent;Al2O3target. The resistivity of the AZO film prepared with the 3 wt &percent;Al2O3target is∼4.7×10−4&OHgr; cm, and depends mainly on the carrier concentration. The optical transmittance of a 1500-Å-thick film at 550 nm is∼90&percent;. The optical band gap depends on the Al doping level and on the microstructure of the films, and is in the range of 3.46–3.54 eV. The optical band gap widening is proportional to the one-third power of the carrier concentration. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365556

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The texture of evaporated Ag films prepared on Ti or Cr underlayers before and after encapsulation process has been studied by x-ray diffraction. In addition, the stress state in self-encapsulated Ag/Ti structures has also been investigated using a “sin2 &psgr;” technique. Silver films deposited on Ti layers exhibit a strong ⟨111⟩ texture, which is in contrast to the nearly random orientation of Ag films on Cr underlayers. The minimization of interfacial energy with respect to lattice match can account for this underlayer dependence. After an encapsulation process involving Ti reactions in an ammonia ambient, the texture of Ag films in Ag/Ti bilayers is further enhanced. Highly textured Ag films may provide the basis for electromigration-resistant Ag metallization in integrated circuit devices. For the Ag/Ti bilayer structures, a low tensile stress of approximately 61 MPa arising from the nonequilibrium growth during the film deposition is present in the Ag films. This results in a lattice tension state in the film plane and a lattice compression state along the film normal. Thermal mismatch stress is produced by the encapsulation process at 600 °C. Most of this stress relaxes during the cooling stage and a residual tensile stress of ∼320 MPa in the film plane was determined. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365386

出版商:AIP    

年代:1997

数据来源: AIP