摘要:

We have used high‐resolution angle‐dependent x‐ray photoemission to study the evolving interface formed by vapor depositing Ge (0–80 Å) onto cured polyimide (PI). The core level line‐shape changes of PI and Ge demonstrate that Ge reacts chemically with PI for coverages below ∼10 Å. The rapid attenuation of the carbonyl C 1sphotoemission intensity shows that Ge reaction preferentially occurs with carbonyl groups for Ge deposition below ∼0.5 Å and charge withdrawal from the imide–benzene ring is reduced. With increasing Ge deposition (between 0.5 and 5 Å), more carbonyl groups are involved in reaction with Ge and the excess of charge carried by carbonyl carbon atoms induces a hyperconjugation form of the imide–benzene ring. These rings are more vulnerable to Ge chemical attack and the formation of Ge–C bonds. Our results indicate multiple Ge–O–C and Ge–C bonding configurations. Once the initial reaction is complete, the growth mode of Ge on PI appears to be layer‐by‐layer‐like. Time‐ and temperature‐dependent x‐ray photoelectron spectroscopy studies of the 40‐Å Ge/PI interface showed no changes below 400 °C. At 400 °C, changes in core level emission intensities indicate clustering and slight intermixing at the interface.

ISSN:0734-2101    

DOI:10.1116/1.575008

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

A new method is described to measure bond lengths in the interface between thin layers, by using multilayered reflection coatings both as a dispersive element in an x‐ray beam, and as an object of measurement. Extended x‐ray absorption fine‐structure (EXAFS) oscillations can be observed in the reflected spectrum. From multilayered Ni/C and NixSiy/C reflection coatings mounted in a double‐crystal monochromator we determined, from these oscillations above the Ni LII,IIIedge, bond lengths equal to 1.8, 2.1, and 2.3 Å, which can be assigned to Ni–C, Ni–Si, and Ni–Ni, respectively. NixSiy/C coatings deposited in a 10−6Torr H2atmosphere show better resolution than those without. The difference is ascribed to H2preventing the formation of silicides and the diffusion of the Ni into the carbon; this results in more amorphous layers. A new and simple method is described for obtaining, in the EXAFS analysis, a high‐resolution radial distribution function (RDF) from a smallk‐vector space chi function. This method is applied to a chi function with one and a half oscillations, yielding a zero dc‐component RDF.

ISSN:0734-2101    

DOI:10.1116/1.575009

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

In this paper we describe a detailed experimental and theoretical investigation of the initial stages of formation of the metal/polyimide interface. Core and valence level spectroscopies combined withabinitioquantum‐chemical calculations have permitted a unique interpretation of the interface growth in terms of charge transfer complex formation between the deposited metal atom and the underlying polymer. The detailed evidence as well as implications concerning metal layer adhesion will be discussed.

ISSN:0734-2101    

DOI:10.1116/1.575010

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We used cross‐sectional transmission electron microscopy techniques to investigate the microstructure of metal/polyimide interfaces. By comparing our results with previously obtained spectroscopy data, we show that the microstructure of these interfaces is strongly related to the tendency of the metal to chemically react with the polyimide at the interface. Cu and Ni do not react with the polyimide and are seen to diffuse inside of the films and form metallic precipitates in the films. Cr reacts with the polyimide at the interface and is thus bounded at the surface, forming a continuous layer on top of the polyimide. Computer simulations are presented that explain the experiment in terms of the different metal–metal and metal–polymer interactions.

ISSN:0734-2101    

DOI:10.1116/1.575011

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Surface chemical modification of polymer thin films induced by sputter etching was studied by x‐ray photoelectron spectroscopy (XPS) and infrared reflection–absorption spectroscopy (IRRAS). The polymers studied were polystyrene, polypropylene, and poly(ethylene terephthalate) (PET). Oxygen and argon sputter etching of these polymers causes surface oxidation and possibly crosslinking; trends in polymer oxidation can be correlated with the etchant gas, etch power, and initial material properties. For polystyrene and polypropylene, the predominant new functionalities formed are C=O and C–O groups; the breadth of the infrared absorption bands suggests that many different types of these groups exist. For PET, the predominant damage mechanism is crosslinking, with only a slight degree of oxidation resulting from oxygen sputter etching. This work suggests that the information provided by XPS and IRRAS is highly complimentary and will be useful in future studies of polymer functionalization and derivatization.

ISSN:0734-2101    

DOI:10.1116/1.575013

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Poly(methyl methacrylate) (PMMA) films of approximately 2.5 μm have been irradiated to various doses using Al x rays. The effect of this irradiation is shown by monitoring the variation in intensity of the Raman vibrational bands of the major constituent species of PMMA, as a function of dose. It is shown that at low doses the molecular weight is reduced as a consequence of main chain scission arising from abstraction of the ester group. This substantiates the previously reported increase in dissolution rate in this dose regime. However, at larger doses it is shown that a cross‐linking reaction generated primary C=C bonds between chain molecules at end‐group sites previously activated by the scission process. This is believed to increase the molecular weight of the polymer resist at larger doses and explains the previously reported drop in the resist dissolution rate at large x‐ray doses. The Raman data suggest that scission and cross‐linking proceed concurrently in response to incident radiation. A model to predict the dissolution rate of the resist as a function of dose based on this dependence of cross‐linking on scission is presented. The results generated from this model are compared to our previously reported experimental resist dissolution data to substantiate conclusions drawn from the Raman results.

ISSN:0734-2101    

DOI:10.1116/1.575014

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Graphite is the primary candidate for the first wall of magnetically confined fusion devices. For this purpose, it is important to know the surface properties of graphite to understand the plasma–surface interactions as well as vacuum properties of graphite. From this viewpoint, we examined the binding states of carbon atoms, inherent hydrogen content, and crystallinity of the surfaces of isotropic graphites prepared by several Japanese companies as well as anisotropic ones with x‐ray photoelectron (XPS), secondary ion mass (SIMS), and Raman (RS) spectroscopies. Although no measurable difference in the binding state of carbon atoms was detected among the isotropic and anisotropic graphites with XPS, RS revealed that their crystallite sizes differed from each other. Namely, the crystallite sizes of the isotropic graphites were in the range from 100 to 300 Å, whereas those of the anisotropic graphites were more than ∼1000 Å. In addition, nongraphitized carbon which was not observed for the anisotropic graphites was present in the surface layers of the isotropic ones. SIMS revealed that the inherent hydrogen contents in the isotropic graphites were larger than those in the anisotropic ones. The results indicate that the larger hydrogen contents in the isotropic graphites are due to the presence of nongraphitized carbon which acts as the trapping site of hydrogen atoms.

ISSN:0734-2101    

DOI:10.1116/1.575016

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

An x‐ray photoemission (XPS) decomposition method has been applied to the oxidation of GaAs(1̄1̄1̄) surfaces, in order to identify the oxidation states. The method, which is based on Fourier transform theory, provides separation of overlap composite spectra into its individual components. The incorporation of truncation techniques, which reduces the spurious structure, allows its application to real unresolved As, Ga, and oxygen core level XPS spectra of oxidized GaAs surfaces. The calculated number and chemical shifts of the Ga and As oxide compounds are in very good agreement with the results obtained by the synthesis method. At least three different forms of bound oxygen, β2, β1, and O=, with chemical shifts of −0.7 eV for the β2and 0.9 eV for the O=referred to the β1state, are resolved in the oxygen (1s) XPS spectra.

ISSN:0734-2101    

DOI:10.1116/1.575017

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The84AsBe−molecular ions under Cs+bombardment were used to detect Be atoms in AlGaAs/GaAs heterostructures. They showed a negligible matrix dependence, compared to that of the9Be+ions under O+2bombardment. The suppressed matrix effect in the former case provided a more straightforward and accurate way for secondary ion mass spectrometry quantification.

ISSN:0734-2101    

DOI:10.1116/1.575018

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The defect density profile of high‐efficiency epitaxial metalorganic chemical vapor deposition (MOCVD) grown GaAs heterojunction solar cell structures has been characterized using a variable‐energy positron beam. Spatial defect changes, film thickness variations, and possibly interfacial space charge and disorder may be resolved from annihilation characteristics by control of the implantation depth of positrons. Correlations were made relating positron annihilation spectroscopy (PAS) measurements to surface photovoltage data, band bending, and known MOCVD growth parameter variations. Based upon these correlations, it is expected that PAS may provide a valuable means for probing defect profiles that may affect the electrical and optical response of MOCVD‐grown semiconductor materials.

ISSN:0734-2101    

DOI:10.1116/1.575019

出版商:American Vacuum Society    

年代:1988

数据来源: AIP