摘要:

We have demonstrated that nanometer‐scale gold dots can be deposited on a vicinal Si(111) 7×7 surface using the field‐assisted atom transfer from the gold‐coated tungsten tip of a scanning tunneling microscope operating in ultrahigh vacuum. With the application of negative voltage pulses to the tip, gold nano‐mounds with the size ranging from ∼3 to ∼20 nm across at the base and 0.6–1 nm high can be created on the surface. The deposition is found to be more favored on the step edges than the (111) terraces. Since atomically resolved images of the Si(111) 7×7 structure can be observed even after many cycles of atom transfer using the gold‐coated tip, the shape of the tip apex has been kept very stable. The overall findings clearly suggest that the atom‐transfer technique proposed here is proven to be a good candidate for fabricating nanometer‐scale devices.

ISSN:0734-211X    

DOI:10.1116/1.588772

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Two‐dimensional periodic arrays containing 108Si pillars with heights of 600–700 nm, widths of 100 nm, and repeat spacings of 300 nm have been fabricated using electron beam lithography on Si(001) substrates. These pillars have subsequently undergone wet oxidation at 800 °C and etching in hydrofluoric acid to produce an array of sharp tips with a height of ∼4000 Å. The x‐ray diffraction from this array appears to be dominated by scattering from the bases of the tips. Correlated variations in tip shape, observed with scanning electron microscopy, produce a modulated diffuse background in the diffracted x‐ray intensity. These observations demonstrate the feasibility of using high‐resolution x‐ray diffraction for studying defects in large‐area arrays of periodic structures.

ISSN:0734-211X    

DOI:10.1116/1.588773

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Atomic force microscopy (AFM) is increasingly relied on to image and measure micron and submicron scale surface features. Consistent interpretation of AFM information is, however, difficult if the geometry of the probe is not known. In this work, the fabrication of funnel‐like structures and their use in probe characterization were developed from a proof of concept to readiness for field testing. The specifications that determine the structure’s sensitivity to probe shape were identified. The fabrication was tailored to yield large reproducible arrays (>100×100 structure). The geometry of the structures was characterized using low voltage scanning electron microscopy (SEM) techniques. Testing in intermittent contact mode has shown that the structures are stable even at high forces for multiple scans under various conditions. An algorithm was developed that calculates the probe geometry from an image of the structure. The sensitivity of the structures to probe shape was tested by comparing SEM images of probe shape to the probe geometry calculated from the AFM images of the structures. From this analysis it was determined that the structures are sensitive to the cone angle of the probe to within 5° and to the probe radius to within 50 nm.

ISSN:0734-211X    

DOI:10.1116/1.588774

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Atomic force microscopy images of porous silicon samples prepared with different conditions have been correlated with photoluminescence (PL) and Raman spectra, allowing a clear classification of two types of samples, ‘‘gently’’ etched versus ‘‘heavily’’ etched. The gently etched samples show a significantly improved morphology and uniformity, as well as consistent correlation in PL and Raman results with the quantum confinement model for the light emission.

ISSN:0734-211X    

DOI:10.1116/1.588775

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Variable angle of incidence spectroscopic ellipsometry, reflectance, and transmittance techniques were used to determine the optical constants of a fluorine doped tin oxide film deposited by chemical vapor deposition onto a hot soda‐lime‐silica glass ribbon. To improve the optical characterization, an additional analytical technique, atomic force microscopy (AFM), was used to incorporate information about surface roughness into the optical model. Our earlier work demonstrated the necessity of including a surface roughness layer as six sublayers in the optical model. The present work further confirms the method and demonstrates its accuracy with additional analytical techniques. These include: (1) cross sectional in‐lens field emission scanning electron microscopy to measure total film thickness, determine presence of interface roughness and extent of surface roughness; (2) secondary ion mass spectrometry to give a first approximation of the film layer structure for optical modeling by depth profiling the film composition; (3) Hall measurements to identify the semiconductor carrier density and mobility; (4) x‐ray diffraction to identify the crystalline phase and preferential growth orientation. The use of AFM surface images and surface roughness plus the other compositional and structural information to improve ellipsometric modeling of thin films has been confirmed.

ISSN:0734-211X    

DOI:10.1116/1.588776

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

A procedure for removing cumulative drift and white noise from scanning probe microscope images has been constructed. Smooth amorphous carbon overcoats on superpolished hard disk media in particular were examined using a scanning probe microscope. The surfaces typically had a ∼1 nm rms roughness over a scan length of 10 μm. The low roughness yielded a relatively low signal to noise ratio in the unfiltered image. While a conventional filter removes a great deal of noise, an optimal Fourier (Wiener) filter that more selectively removes noise from the image is discussed. White noise and drift were modeled and their contributions to the power spectrum are estimated, resulting in an open clamshell‐shaped two‐dimensional filter. The effect of the filter was demonstrated by subjecting filtered images of unworn and worn areas to a smooth surface to second derivative calculations in different directions. Anisotropy in the wear process associated with the wear direction is apparent in the optimally filtered images.

ISSN:0734-211X    

DOI:10.1116/1.588777

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Atomic structures of Ag2Te in the low‐ and high‐temperature phases have been studied using a scanning tunneling microscope in air and an x‐ray diffraction system. In the low‐temperature phase having a monoclinic lattice, (001) and (01̄0) atomic images are obtained. In the superionic high‐temperature phase, which is stable at temperatures above 145 °C, (100) surfaces of the Te cubic lattice are observed. In both phases, surface atomic reconstructions are not detected.

ISSN:0734-211X    

DOI:10.1116/1.588778

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Results of beam collimation experiments on linear field‐emitter arrays with linear planar lenses are summarized. The electron beam is imaged on a phosphor screen. In general, as lens voltage is reduced relative to the gate voltage, the elliptically shaped screen images narrow, becoming fine lines with emission currents showing only modest reductions. This reduction of emission current can be overcome by increasing the gate voltage only a few volts without affecting beam collimation. As the lens voltage is reduced, screen current decreases relative to emission current while gate current increases, indicating that some emitted electrons in this linear lens geometry cannot propagate to the anode screen. Experimental data and qualitative modeling are in fair agreement.

ISSN:0734-211X    

DOI:10.1116/1.588779

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The Brillouin light scattering technique has been used to study the elastic properties of a number of silicon dioxide films deposited by plasma‐enhanced chemical vapor deposition on Si substrates. In addition to stoichiometric undoped glass films produced from either silane or tetraethylorthosilicate, we have also studied nonstoichiometric Si‐rich films andP‐doped films. The phase velocity of both the surface Rayleigh mode and the longitudinal bulk wave in the film material has been measured and the two independent elastic constantsc11andc44have been evaluated. The derived values of the Young modulus and the Poisson ratio show appreciable deviations from the values we measured on thermally grown oxide. Moreover, the evolution of the stress during thermal cycles has been analyzed using the substrate curvature method. This permitted us to estimate the thermal expansion coefficient of the films and to distinguish between the intrinsic and thermal components of the stress.

ISSN:0734-211X    

DOI:10.1116/1.588780

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The incorporation and distribution of nitrogen in ammonia nitrided thermal polyoxide (NPOX) dielectric films and their degradation durability to reduced pressure, dichlorosilane (SiH2Cl2)–HCl–H2ambient during epitaxial lateral overgrowth (ELO) indicated that the surface nitrogen concentration had no effect. However, a bulk nitrogen concentration as low as 8 at. % significantly reduced the formation of ELO ambient induced pinholes in 250 Å polyoxide films. After 40 min of ELO ambient stress the electrical yield was raised from 0%, for the control polyoxide dielectric capacitors, to 84% for NPOX dielectric capacitors. Analyses of the failed devices suggest that active pinhole generation still exists, however, the bulk nitrogen concentration dramatically reduces the frequency and rate at which these dielectric defects are produced.

ISSN:0734-211X    

DOI:10.1116/1.588781

出版商:American Vacuum Society    

年代:1996

数据来源: AIP