摘要:

The electrostatic energy between a dielectric scanning force microscope (SFM) tip and a point charge is obtained in closed form as a function of the separation of the two objects. Applications of this result to both spherical and arbitrary tip shapes are discussed. Also, utilizing kinematic data, a method is given to experimentally extract the force due to the tip-sample interaction from a typical SFM instrument. This is done by analyzing the time dependent motion of the tip. The result is based on the use of a time dependent analysis of the force distance curve which is unavoidable in motion regimes in which the tip accelerates, as in the snap-to-contact process.

ISSN:1071-1023    

DOI:10.1116/1.589567

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

We report results of the measurement of local work function, or apparent barrier height, on the Au/Cu(111) surface using scanning tunneling microscopy (STM). By measuring a response of tunneling current to a change of the tunneling gap distance during scanning, we can obtain a work function image simultaneously with a topographic STM image. In this way, we could successfully observe the difference in local work function due to different elements and atomic structures. Our results show that the mean work function value of the Au overlayer is7±3%larger than that of the Cu(111) substrate and the value of the work function of the second Au layer is the same as that of the first Au layers within the measurement uncertainty. At the step edges, the work function values are lower than that on the terrace. The width and depth of the low work function trough at Au–Au, and Cu–Au single height steps were also obtained. The measured values are consistent with those measured on vicinal surfaces. This work also suggests that the local work function measurement can be used to identify the element on a surface and that the STM is quite useful to get information on how the work function is related with surface structures and how the work function spatially changes on nanometer scales.

ISSN:1071-1023    

DOI:10.1116/1.589568

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Morphological changes of sputter-deposited TiN films in 0.1 M sulphuric acid have been followedin situwith scanning force microscopy at different potentials. Disappearance of small structures was observed with increasing potential up to 1.2 V. A further increase of potential above 1.5 V resulted in growth of larger grains. Two passivation peaks at about 0.6 and 1.2 V, respectively, were recorded for the TiN films. The passivating layers formed at these two passivation peaks were characterized by x-ray photoelectron spectroscopy. At the lower passivation peak, titanium suboxides or oxynitrides were detected, whileTiO2was formed at potentials above 1.2 V.

ISSN:1071-1023    

DOI:10.1116/1.589569

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

This article has successfully demonstrated for the first time a chemical reaction induced by a resistive thermal tip. The resulting structures were subsequently imaged by scanning thermal microscopy (SThM) and atomic force microscopy. The thermal conductivity contrast in SThM images suggested that palladium acetate thin film could be decomposed to palladium metal. The resulting palladium metallic features can form down to the substrate and adhere well on the substrate by using thinner precursor palladium acetate film. The effect of control resistance and tip scan rate on resulting features has also been studied. The results obtained indicate the potential application of SThM tip induced chemical reaction in device fabrication.

ISSN:1071-1023    

DOI:10.1116/1.589570

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

A detailed study of tunneling spectroscopy concerning semiconductors with a low surface state density is presented. For this purpose,I–Vcurves under dark conditions and under illumination were measured on the (0001) van der Waals surface of ap-typeWS2single crystal, which is known to be free of intrinsic surface states. The measurements are interpreted by an analytical one-dimensional metal-insulator-semiconductor model, which shows that the presence of the finite tunneling current has to be considered in the calculation of the tip-induced bandbending. Rectification of the darkI–Vcurves is explained by the absence of an inversion layer at the semiconductor surface. In contrast, theI–Vcurves measured for different light intensities and tip-sample separations indicate the existence of an optically induced inversion layer. Since no surface recombination needs to be considered to model these spectra, we conclude that bulk recombination, diffusion and direct tunneling of photogenerated minority charge carriers are the dominant processes for semiconductors with a low density of surface states. In contrast to the standard interpretation of tunneling spectroscopy, which can be applied to semiconductors with a high surface state density, our results clearly show that in this case the normalized differential conductivity(dI/dU)/(I/U)cannot be used to determine the energetic distribution of the local surface state density.

ISSN:1071-1023    

DOI:10.1116/1.589571

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

The applicability of scanning probe microscopy in the dielectric breakdown characteristics of silicon oxide has been demonstrated. Our study demonstrates that the measurement on the oxide is free from the effect of trapped charge created by Fowler–Nordheim tunneling when a sufficient distance is maintained between the measuring points. In this condition, for a 13-nm-thick oxide, the dielectric breakdown voltages were found to be so uniform as to fluctuate only 1%. We applied this method to oxides on the wafers from two different vendors, and found that the dielectric breakdown strength of the oxide depends on the difference on the Si substrates. We also applied this method to a square oxide pattern surrounded by a field oxide, and the result was that the dielectric breakdown strength of the oxide on the edge is lower than the one in the center.

ISSN:1071-1023    

DOI:10.1116/1.589572

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

In this article, nanometer-sizedIn2O3organosol capped with a layer of anionic surfactants was prepared using microemulsion method. Its structure and optical properties were investigated through transmission electron microscopy, ultraviolet-visible absorption spectra, photoluminescence spectra andZ-scan technique. It was found that the preparedIn2O3organosol showed a series of new optical properties, which can be explained by its special oxygen vacancy structure. These new optical properties enhance its applications in information optics.

ISSN:1071-1023    

DOI:10.1116/1.589573

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

The evolution of surface morphology in the initial stage of nitridation of Si(111)-7×7has been investigated by using a scanning tunneling microscope (STM) and low energy electron diffraction (LEED). The STM and LEED measurements were done on the Si(111) surface nitrided under different experimental conditions including the variations in the nitrogen ion energy, nitrogen ion dose, nitridation temperature, and the postannealing temperature. A growth mechanism of the silicon nitride layer in the initial stage was proposed based upon a comparison of the surface morphology obtained under different nitridation conditions. For the growth of uniform and large silicon nitride islands, it was necessary to have proper heat treatment of the surface. In particular, the surface postannealed at 980 °C after nitridation at 950 °C produced dramatically enlarged flat silicon nitride islands compared to that postannealed at the same temperature after nitridation at room temperature, and is probably due to improved mobilities of the reacting species with elevation of the nitridation temperature.

ISSN:1071-1023    

DOI:10.1116/1.589574

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

We have measured Fourier transform infrared (FTIR) spectra ofCr3+immersed porous silicon after annealing at different temperatures. After dipping porous silicon intoCr3+solution, three additional peaks appear at 807, 886, and940 cm−1in the FTIR spectrum. When annealed in nitrogen at different temperatures for various durations, the peak at807 cm−1remains almost unchanged, the height of peak886 cm−1decreases gradually, while the peak at940 cm−1disappears quickly. This decay process occurs much faster at higher annealing temperature. These FTIR features reflect the surface chemistry change after immersed intoCr3+solution.

ISSN:1071-1023    

DOI:10.1116/1.589575

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

A semiempirical expression was developed for the growth rate of selective epitaxial growth (SEG) and epitaxial lateral overgrowth of silicon in a rf heated cold-wall low pressure chemical vapor deposition pancake reactor for the dichlorosilane-HCl–H2system. The model was obtained for temperatures ranging from 920 to 1020 °C, system pressures from 40 to 150 Torr, and over a range of HCl and dichlorosilane gas flows. The growth rate expression is the sum of a growth term which is a function of the partial pressures of dichlorosilane(SiCl2H2)and hydrogen, and an etch term that varies with the partial pressure of HCl. The growth and etch terms have a temperature Arrhenius relation with activation energies ofEgr=2.266andEet=1.349 eV,respectively. Included is a term to account for the SEG growth rate dependence on the ratio ofSiO2area coverage to silicon wafer area. A methodology was developed for obtaining the coefficients for the semiempirical growth rate expression from several sets of experiments.

ISSN:1071-1023    

DOI:10.1116/1.589576

出版商:American Vacuum Society    

年代:1997

数据来源: AIP