摘要:

We have synthesized superconducting YBa2Cu3Oxthin filmsinsituusing magnetron cosputtering with three metallic targets (Y, Ba, Cu). We present details of the sputtering chamber, as well as the growth conditions necessary to obtain superconducting films. We discuss the effects of oxygen and ozone partial pressure, differential pumping, O2–Ar plasma deposition and Ba–Cu alloy targets. We elaborate on our ozone condensing and delivery system. Finally, we describe the difficulties encountered with the deposition system and provide details of possible improvements.

ISSN:0734-2101    

DOI:10.1116/1.578070

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Strontium titanate (SrTiO3) thin films on silicon wafers were grown by radio frequency (rf) magnetron sputtering at various growth conditions. The films were characterized using x‐ray diffraction (XRD), infrared (IR) spectroscopy, and scanning electron microscopy (SEM). The films deposited below 200 °C were amorphous state and above 300 °C were crystalline state according to XRD and IR spectroscopy. The surface of strontium titanate film deposited at room temperature was smooth and those deposited at higher substrate temperatures showed discernible grains of which size were increased with increasing substrate temperature. By annealing at 600 °C in oxygen atmosphere, the amorphous strontium titanate were crystallized and the grain size of the films were increased. The deposition rate of the films were investigated by the growth parameters such as substrate temperature, Ar–O2gas composition, and rf power.

ISSN:0734-2101    

DOI:10.1116/1.578071

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

An apparatus for direct current ion beam sputtering is described which incorporates some new features, specifically with respect to target and plasma current control. In conjunction with a radiotracer technique it is demonstrated how resolution and sensitivity of depth profiling can be substantially enhanced by reduction of the ion energy and correction for after effects in sputtering. Investigations of metal diffusion in polymers and isotope effect measurements in metallic glasses are presented as examples.

ISSN:0734-2101    

DOI:10.1116/1.578072

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

A computer‐aided method to improve the thickness uniformity attainable when coating multiple substrates inside a thermal evaporation physical vapor deposition unit is presented. The study is developed for the classical spherical (dome‐shaped) calotte and also for a plane sector reversible holder setup. This second arrangement is very useful for coating both sides of the substrate, such as antireflection multilayers on lenses. The design of static correcting shutters for both kinds of configurations is also discussed. Some results of using the method are presented as an illustration.

ISSN:0734-2101    

DOI:10.1116/1.578073

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The specific contact resistant ρCof In contacts ton‐Hg1−xCdxTe has been measured as a function of the Cd mole fraction and annealing treatment of the Hg1−xCdxTe. Transmission line model measurements were performed on the In/Hg1−xCdxTe junctions with the Hg1−xCdxTe dopedntype in the range 3.5×1016to 1.6×1018cm−3(77 K). A linear dependence of In ρConxwas obtained, with values of ρCranging from 2.0×10−5Ω cm2atx=0.30 through to 2.6×10−2Ω cm2atx=0.68. Hg annealing of the epitaxial Hg0.38Cd0.62Te layers resulted in a decrease in ρCfrom 5.9×10−3Ω cm2unannealed to 1.2×10−3Ω cm2after a 300 °C anneal, corresponding to equivalent changes in the resistivity of the Hg1−xCdxTe. Isothermal annealing of the In/n‐Hg1−xCdxTe contacts forx=0.30, 0.40, and 0.62 produced an enhanced indiffusion of In but with only a minor reduction in ρC.

ISSN:0734-2101    

DOI:10.1116/1.578121

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

This article first describes the preparation and properties of small area (∼1 μm2)Pb/Bi/In‐oxide–Ag junctions made by evaporation through metal masks. These junctions have successfully been used in a 230 GHz receiver. We then describe the preparation and properties of two slightly different types of Nb/Al‐based superconductor–insulator–normal conductor (SIN) junctions applying a ‘‘trilayer technique’’ similar to that used in the fabrication of Nb–Al‐oxide–Nb superconductor–insulator–superconductor junctions. For one type of the Nb/Al‐based SIN junctions the base layer consists of Nb, for the other type, the base layer is made of Al. In practical applications these devices will operate at temperatures where the Al is in the normal state. Junctions with areas down to about 0.5 μm2have been made.

ISSN:0734-2101    

DOI:10.1116/1.578122

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Reported here are studies in which an oriented single‐crystal, Hg0.8Cd0.2Te (111), was etched with methanolic bromine solution, ion bombarded with Ar+, and annealed in Hg vapor. Both parallel faces of the crystal, the metal‐terminated (111)A surface and the Te‐terminated (111)B surface, were characterized after each of the above stages of preparation by Auger electron spectroscopy (AES), electron energy‐loss spectroscopy (EELS) and low‐energy electron diffraction (LEED). After polishing in air the (111)A and (111)B surfaces were found to be contaminated with C and S‐containing substances, and deficient in Cd; the LEED patterns were diffuse. EELS spectra showed a broad C–H stretching band near 2980 cm−1and another broad band centered at 1300 cm−1due to C–H bending and C–C stretching of surface hydrocarbons. Etching with bromine solution in air removed S‐containing surface contaminants, without significantly changing the LEED and EELS results. Argon ion‐bombardment removed the C contamination and increased the Cd content to expected levels, while decreasing the Hg content substantially. LEED showed a (111)A[1×1] pattern with strong diffuse scattering, while the (111)B[1×1]pattern was comparatively weak, indicating that detectable long‐range order existed somewhere within the outermost few atomic layers. EELS of both faces displayed a peak at about 140 cm−1attributable to the excitation of surface phonons. When the ion‐bombarded crystal was annealed in Hg vapor, the Hg surface concentration increased. The ratios of metal to Te Auger intensity (IHg/ITeandICd/ITe) were larger for the (111)A than for the (111)B surface. The A‐face yielded a sharp (2×2) LEED pattern, while the B‐face displayed a reproducible, complex, three‐fold symmetric pattern indicative of a faceted surface. The annealed surfaces exhibited virtually the same EELS spectra as bombarded surfaces. The annealed surfaces are stable in vacuum, as judged by AES, LEED, and EELS.

ISSN:0734-2101    

DOI:10.1116/1.578124

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

We report a photoreflectance study of Fermi level pinning (VF) on (001)n‐ andp‐type GaAs with large, uniform electric fields. Surface photovoltage (Vs) effects were evaluated as a function of temperature (77K

ISSN:0734-2101    

DOI:10.1116/1.578125

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Electron energy loss spectroscopy (EELS), Auger analysis and Auger line shape measurements were used to study composition and bonding in thin films of varying Al:N:O ratios grown by reactive magnetron sputter deposition. The films deposited in the presence of oxygen in addition to nitrogen or ammonia in the plasma are apparently composed of both AlN and Al2O3. There is no evidence for other bonding configurations. In accordance, the observed ionicity of the Al–N and Al–O bonds is the same as in the respective single‐phase films. The AlN and Al2O3phases are clearly distinguished by their Al(LVV) signals, but not by the respective Al(KLL) transitions. A relative sensitivity factor of Al(KLL) in the AlN thin films at a primary energy of 3 keV was obtained from analyses of both AlN and (AlN)x(Al2O3)1−x. The same sensitivity factors of Al(KLL), N(KLL), and O(KLL) are adequate for analysis of both single‐ and two‐phase films. The EELS in the 4–40 eV range at primary energies of 135 and 185 eV contain unresolved contributions from both AlN and Al2O3. Results are compared to those of Al2O3, thin films of oxidized and nitrided Al, and NO exposed Al(100) surface. Bonding at the latter surface appears to differ from that at the two‐phase films. Charging and stability effects in the films are also discussed.

ISSN:0734-2101    

DOI:10.1116/1.578126

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Tungsten/carbon (W/C) multilayer thin films were prepared by dc magnetron sputtering. All samples consisted of 30 layer pairs with a nominaldspacing varying from 2.5 to 14 nm, the W layer thickness was kept at 2 nm in all samples. The W/C multilayers were subjected to isochronal anneals in a quartz tube furnace at the temperature range from 500 to 950 °C under a flow of high purity Ar gas. X‐ray diffraction, Raman scattering, and Auger depth profile were used to characterize the structure of the as‐prepared and annealed multilayer films. Both the W and C layers appear to be amorphous as‐prepared. An overcoat of 30 nm of plasma enhanced chemical vapor deposited silicon nitride was found to inhibit oxidation during annealing. For those multilayers containing thinner carbon layers (<1 nm), the formation of crystalline W2C occurs at annealing temperature as low as 500 °C and a very small expansion (<2%) in the layerdspacing is observed. On the other hand, for all multilayers with carbon layer thickness equal or greater than 2 nm, crystallization occurs at much higher annealing temperatures and the crystalline phases observed were alpha‐W and WC. It is also observed that in the latter group the period increases monotonically with increasing annealing temperature, the total expansion is about 10% and affects both W and C layers approximately equally. The expansion stops at the crystallization temperature which occurs at 900 °C or higher. The expansion is under investigation but may be interpreted as due to the structural ordering processes in the amorphous W and C layers.

ISSN:0734-2101    

DOI:10.1116/1.578127

出版商:American Vacuum Society    

年代:1992

数据来源: AIP