摘要:

Films were sputter deposited from a Ni/Cr target (4:1 weight ratio) in an oxygen plasma onto polyimide substrates. The films are black in color, and show excellent adhesion and flexibility. Comparison of x‐ray photoelectron spectra of 1.7 μm‐ and 3.5 μm‐thick coatings of oxidized Ni/Cr with a control coating of oxidized Ni (i.e., presumably NiO) suggests that the presence of the Cr correlates with the formation of at least one nickel species other than NiO. As the oxidized Ni/Cr film thickness varies from 0.13 to 3.5 μm, the absorptance and emittance vary from 0.78 to 0.89, and from 0.27 to 0.62, respectively. Using a model proposed by Thakur, it is calculated that for the thicker films the emitted radiation has a wavelength of approximately 7 or 8 μm.

ISSN:0734-2101    

DOI:10.1116/1.577154

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

High‐resolution x‐ray photoelectron spectroscopy has been applied to study the formation of the merocyanine/aluminum interface. It is concluded that merocyanine exists in zwitterionic form and aluminum bonds with merocyanine at−O–C– and C=O in carbonyl group, forming the complex compound of C–O–Al. The attenuation curves of C,N,O,S exhibit the cluster growth of aluminum, which preferentially resides on heterocycles. The temperature effect on merocyanine/Al interface is also investigated in detail.

ISSN:0734-2101    

DOI:10.1116/1.577155

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The change in chemical structure of the top surface layer of thin poly(methylmethacrylate) (PMMA) and polyimide (PI) films (200–1500 Å) during downstream microwave NF3/CF4/O2plasma etching are investigated byinsituFourier transform infrared (FTIR) reflection–absorption spectroscopy. Plasma fluorination of PI by either NF3or CF4leads to significant surface fluorination characterized by the formation of aliphatic fluorine compounds (CFx), acyl fluoride, benzoyl fluoride, acyl hypofluorite, and polyfluorinated benzene. The surface fluorination process is found to be controlled by diffusion in the product layer and the depth of fluorination is estimated from infrared absorbance to be approximately 500 Å. Addition of oxygen leads to a reduction in the fluoride species and the development of broad absorption bands representing oxygenated surface species. The FTIR data are supplemented byexsitux‐ray photoelectron spectroscopy observations and mechanisms for the observed modifications of the polymer surfaces are proposed. The effect of humidity on the plasma‐modified polymers is studied by comparing infrared spectra collectedinsituafter controlled exposure to moisture. PI fluorinated in NF3show no significant changes, whereas a slow but noticeable change in the carbonyl bands is detected for NF3/Ar plasma‐fluorinated PMMA. Addition of oxygen to the microwave plasma increases the sensitivity of the modified polymer to moisture. These observations are interpreted in terms of the wettability of the polymer surface.

ISSN:0734-2101    

DOI:10.1116/1.577156

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The role of oxygen in affecting the adhesive bonding at the metal/polyimide (polyimide‐on‐metal) interface has been studied. Both pyromellitic dianhydride (PMDA) ‐oxydianiline (ODA) and biphenyl‐tetracarboxylic dianhydride(BPDA) ‐p‐phenylene diamine (PDA) based poly(amic acid) precursors were cast and fully imidized on metal surfaces of Cr, Cu, Ni, Co, Cu/Ni, and Cu/Co in a nitrogen atmosphere. The peel strengths at the polyimide‐on‐metal interface were measured, using a 90° peel test, immediately after curing, and then remeasured after annealing in either nitrogen (N2−≤100 ppm O2) or air (N2–21% O2) at 350 °C for 1 h. Very little or no change in peel strength was measured after these samples were annealed in nitrogen, while significant adhesion degradations were measured on all metals after annealing in air. The loss of polyimide (PI) adhesion to the Cu or Co surface is attributed to metal catalyzed thermal–oxidative degradation of the PI at the metal/PI interface, as characterized by polyimide thickness reduction, Fourier transform infrared and x‐ray photoelectron spectrometries. The rate of degradation of the PMDA‐ODA films on Cu or Co is several times faster than that of the BPDA‐PDA films.The degradation products were characterized as CO2, CO, Cu carboxylate salts and a nitrile moiety entrapped in partially degraded PI films. The extent of degradation was found to increase with increasing oxygen content in the annealing ambient or with decreasing PI thickness, indicating that oxygen diffusion through the PI overcoating to the metal/PI interface plays a critical role in promoting degradation. On the Cr and Ni surfaces, such metal catalyzed degradation was not detected with our techniques, while some adhesion strength was still retained, a significant loss in adhesion strength was observed. This is probably due to oxidation of the metal underlayer causing debonding at the originally well adhered metal/PI interface. When all testing variables were held constant, the peel strength of a well adhered metal/PI joint is shown to increase with increasing peeling rate (crosshead speed). An increase of up to ∼40% in peel strength was measured when the crosshead speed was increased from a low speed of 0.05 mm/min to 10 mm/min. The locus of fracture of the as‐cured films was cohesive, i.e., the fractured surface was located within PI, while for the thermal–oxidative degraded joint the failure mode was changed to adhesive.

ISSN:0734-2101    

DOI:10.1116/1.577157

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Surfaces of polyethylene and polyimide films were treated in NH3and N2plasma using ‘‘dual‐frequency’’ excitation: The samples were exposed to a microwave (2.45 GHz) glow discharge, while variable radio frequency (13.56 MHz)—induced negative direct current bias voltage values were simultaneously applied. The surface chemical structure was determined by high‐resolution x‐ray photoelectron spectroscopy. Up to 40 at. % of nitrogen was incorporated onto the sample surface by exposure to a microwave discharge in N2, while systematically lower N uptake was found in NH3plasma. Nitrogen was found to be bonded predominantly in amine (C–N) groups by NH3‐type plasma, and in imine groups (C=N) by N2plasma. Surface ‘‘damage’’ of polyimide, including opening of benzene rings and breaking of carbonyl groups, accompanied by the formation of increasing concentrations of chemically reactive receptor sites, has been demonstrated with increasing the energy of bombarding species.

ISSN:0734-2101    

DOI:10.1116/1.577158

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Factor analysis is applied to the Auger crater‐edge profile of a palladium/hydrogenated amorphous silicon layered structure. The results show, apart of a considerable improvement in interface determination, new information not obtainable by the conventional Auger depth profiling technique, which makes this procedure extremely useful for thin film depth profiling.

ISSN:0734-2101    

DOI:10.1116/1.577159

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Amorphous carbon films deposited at near room temperature on Si substrates by a direct current plasma chemical vapor deposition technique using CH4gas have been annealed in vacuum. X‐ray photoelectron spectroscopy measurements show that, as the annealing temperature increases from room temperature to 300 °C, a significant shift (0.5 eV) of the C 1selectron binding energy is observed. The observed shift may be the indication of an atomic structure change of the amorphous films upon the thermal annealing. On the other hand, a large shift in thesp2bond peaks of the Raman spectra only occurs at annealing temperatures higher than 300 °C, which may be the indication of a structural change of the amorphous carbon films by the annealing. A two stage stress release mechanism is suggested: One for the atomic structure change and one for the film structure change.

ISSN:0734-2101    

DOI:10.1116/1.577160

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We discuss the possibility of replacing oxygen with nitrogen trifluoride in the preparation of stable GaAs negative electron affinity (NEA) photocathodes. The different role of O2versus NF3exposure during the activation is examined by means of quantum yield and photocurrent lifetime measurements. Quantum yield results clearly demonstrate that NEA conditions can be attained also with NF3. Measurements performed on the same samples and in the same experimental conditions, show a remarkably different time evolution of the activation process in the two cases. However, as a result of a huge number of activations, no evidence of significantly larger lifetimes for NF3prepared photocathodes can be deduced.

ISSN:0734-2101    

DOI:10.1116/1.577161

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We have investigated methods of chemical preparation and thermal treatments of InSb substrates to produce InSb surfaces suitable for subsequent molecular beam epitaxy. Etching in a solution of lactic acid: HNO3:HCl was shown to produce an oxide surface layer which could be thermally desorbed. Growth on surfaces prepared in this manner produced precipitate‐free substrate–epilayer interfaces.

ISSN:0734-2101    

DOI:10.1116/1.577162

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The wall recombination coefficient (γ) of several materials for atomic oxygen was measured introducing a new method based on the NO*2continuum in a discharge‐flow system. This method has many advantages, such as the ability of measuring γ under different pressures, nonessentiality of measuring absolute atom concentrations, simplicity of experimental technique, etc. over the previous methods. Investigated materials in this work were selected specially considering the feasibility of industrial applications of plasmas. Although a few metals show slight differences, most of the calculated values of γ are in agreement with the literature values. Observed γ for Al and Al based materials were in the order of 10−3. The highest and lowest γ measured were of Cu and teflon, as 2.6×10−2and 7.3×10−5, respectively.

ISSN:0734-2101    

DOI:10.1116/1.577163

出版商:American Vacuum Society    

年代:1991

数据来源: AIP