Papers

AVS2000 Session MC-TuM: Real World Surface Analysis

Tuesday, October 3, 2000 8:20 AM in Room 207

Tuesday Morning

Start	Invited?	Item
8:20 AM		MC-TuM-1 Surface Interaction, Coverage and Performance of Quaternary Amine Treatments on Hair B.C. Beard (Akzo Nobel Chemicals); D. Tang (Akzo Nobel Surfactants America); J. Hare (Akzo Nobel Chemicals) Surface analysis by Xray Photoelectron Spectroscopy (XPS) has shown specific one to one (ionic) interaction between cationic quaternary alkyl conditioning molecules and the anionic sulfonate groups present on the hair surface. Conditioning cationic quaternary molecules incorporating ester and alcohol functionality (ester quat) demonstrate a lower number of surface quaternary nitrogen per sulfonate group, indicating an altered surface interaction mechanism. Relative conditioner surface coverage for the ester quat is not reduced despite the apparent decrease in ionic interaction at the surface. Molecular dynamics modeling of the conditioner-hair surface interaction indicate higher adsorption energies for ester quaternary amine conditioning molecule. Industry standard tests demonstrate the superior performance of ester quats, in keeping with the increased surface coverage.
8:40 AM		MC-TuM-2 Chemical Characterization of Modified Nanotips by TOF-SIMS and Laser-SNMS R. Kamischke, F. Kollmer (Physikalisches Institut der Universitaet Muenster, Germany); R. Stark, W. Heckl (Institut fuer Kristallographie und Mineralogie der Universitaet Muenchen, Germany); A. Benninghoven (Physikalisches Institut der Universitaet Muenster, Germany) For many applications of nanotips detailed information on their chemical surface composition with high sensitivity is a key issue. This holds e.g. for their use as chemical sensors, where the tip surface is chemically modified, or for nanoextraction of sample material by direct contact with the tip. TOF-SIMS and Laser-SNMS are the most sensitive techniques for chemical surface mapping with high lateral resolution. The large fraction of sputtered neutrals and their efficient Laser-postionization results in a high Laser-SNMS sensitivity. In this contribution we summarize and compare results of TOF-SIMS and Laser-SNMS characterization of chemically modified as well as metal loaded Si₃N₄ and Si AFM cantilever tips. All experiments were carried out in a reflectron based time of flight instrument with a fine focused Ga⁺-LMIS (≥80 nm). For nonresonant postionization an excimer laser (248 and 193 nm) was applied. Special efforts had to be put on the sample preparation. Distortion of the extraction field, shadowing effects, charging, and presputtering during sample adjustment had to be reduced to a minimum. On surface modified cantilevers it is not possible to characterize the tip itself, because of the lateral resolution being limited to at best 80 nm. However, imaging the tip pyramid provides detailed information on the surface composition, and in this way on the results of surface modification efforts. For Nanoextraction of metals (Co, Cu, Ag) the sample is imaged by AFM and material is extracted by applying a loading force of several µN and scanning over the surface for some µm. The extracted amount of material adhering to the top of the tip can be characterized down to the sub-amol range. Most important advantages of Laser-SNMS compared to SIMS are enhanced ion yields for elements (≤10^-2), the ease of quantification and the fact that sputtered neutrals are not affected by electrostatic fields in the vicinity of the sample.
9:00 AM		MC-TuM-3 Real World Surface Analysis B. Hagenhoff (TASCON GmbH, Germany) Most surface analytical techniques like photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) have left their academic origins and are routinely applied in university and industry laboratories. Whereas in former times most analyses were performed at model systems having only one or few known compounds, nowadays surface analytical techniques are used to solve daily occurring problems in industrial environments. Materials to be analyzed in these cases mostly contain several components and the respective samples may have undergone additional surface treatments. The talk will concentrate on the special requirements to be dealt with when working on practical problem solving. Issues covered will include sample preparation, selection of the suited analytical technique, set-up of the equipment and data evaluation. Case studies taken from semiconductor and glass industry will be used to explain how both, XPS and TOF-SIMS, can successfully be used to solve "real world" problems.
9:40 AM		MC-TuM-5 Thermal Degradation of IM7/BMI5260 Composite Materials: Characterization by X-ray Photoelectron Spectroscopy S. Ohno, M.-H. Lee, K.Y. Lin, F.S. Ohuchi (University of Washington) High performance polymeric composites (IM7/BMI5260) are being considered for use in structures for high speed aerospace vehicles. In this application, composite components are exposed to elevated temperatures for a long time period. This results in physical and chemical degradation of the polymers. In this paper, experimental studies were conducted to investigate the effects of isothermal aging of the IM7/BMI5260 exposed at 150 - 200°C using x-ray photoelectron spectroscopy (XPS). During the XPS measurements, binding energies for the carbon-fibers are uniquely determined because of their electrically conducting nature, whereas binding energies for the polymeric matrix are shifted by the amount of bias voltage applied to an electron flood gun. This effect turns out to be useful to separate out the contribution from carbon fibers and polymeric matrix, thus we have established a unique experimental protocol to analyze the composite material surfaces. Experimentally, the composite specimens were oxidized in an environmental cell specially designed to mimic the aging conditions, and analyzed to learn intrinsic nature of the chemical reactions. These data were further compared with those obtained from long-aged specimen (7 months at 205 °C in air). Our results indicate that degradation of the IM7/BMI5260 is initiated by preferential oxidation of the carbon sites in the BMI to form the carbonyl species, followed by the oxidation to CO₂ leading to degradation.
10:00 AM		MC-TuM-6 Pt-Metal Oxide Aerogel Catalysts: An X-ray Photoemission Investigation A.J. Nelson, J.G. Reynolds (Lawrence Livermore National Laboratory) X-ray photoemission spectroscopy was used to study Pt-metal oxide aerogel catalysts that have been developed to respond to increased NO_x emissions of lean-burn engines. Lean-burn engines, critical components of low and zero emission vehicles, produce much higher levels of engine-out NO_x and current three-way catalytic converters are not sufficient to meet Clean Air Act standards. Platinum catalysts were formed by the reaction of modified Pt coordination compounds with selected transition-metal alkoxides through sol-gel techniques into aerogels. Photoemission measurements on the valence band electronic structure and Pt 4f, Si 2p, Ti 2p and O 1s core lines were used to evaluate the chemistry of the material after each processing step. Results indicate Pt-O bonding and reduced Pt disbursed in the aerogel. In addition, Si 2p, Ti 2p and O 1s binding energies indicate an oxo-bridged network structure.
10:20 AM		MC-TuM-7 Quantification of the Changes in the Air-formed Oxide/Hydroxide Film at the Surface of Aluminium on Exposure to Ambient Conditions M.R. Alexander, G.E. Thompson (UMIST, UK); G. Beamson (RUSTI, CLRC, UK); A.J. Roberts (Kratos Analytical, UK) The performance of coated and bonded Al is dependent on its surface chemistry. XPS is a powerful tool for characterising of the surface air-formed film. It is apparent that agreement exists in the literature on the method to calculate the oxide thickness from the clearly resolved metal and oxide components of the XPS Al2p core level.¹ However, there is no consensus on the approach for fitting the unresolved oxide and hydroxide components of the O1s, indeed some suggest that it is not advisable.² Recently, a method based on defining the separation between the O1s and Al2p components has been developed using an oxyhydroxide standard.³ Here, the film formed at the surface of magnetron sputtered Al is characterised. Importantly, this sample allows reliable definition of the age of the surface film and control of the alloying elements. Curve fitting of the O1s and Al2p core levels from samples after a range of atmospheric exposure times revealed the gradual formation of hydroxide ions in the surface film, an increase in its thickness and the adsorption of adventitious hydrocarbon. Interestingly, it was determined that atmospheric moisture influences strongly the hydroxyl concentration and the rate of film growth. Changes in the wetting of the surface were measured through the water contact angle, which increased from about 10° to 80° over a 24-h period. This was assigned to the formation of a continuous overlayer of hydrophobic adventitious hydrocarbon onto the hydrophilic oxide/hydroxide surface film. Characterisation of this "ageing" of the Al surface forms the basis for an investigation into the effectiveness of plasma cleaning and the atmospheric stability the resultant surface. ¹ B Strohmeier Surf. Interface Anal. 15 51 (1990). ² PMA Sherwood Surf. Sci. Spect. 5 (1) 1 (1998). ³ MR Alexander, GE Thompson and G Beamson, Surf. Interface Anal., 29 (7) in press (2000).
10:40 AM		MC-TuM-8 Scanning Auger Microscopy Studies of an Ancient Bronze E. Paparazzo (Consiglio Nazionale delle Ricerche, Italy); A.S. Lea, D.R. Baer (Pacific Northwest National Laboratory); J.P. Northover (University of Oxford, UK) We have conducted a scanning Auger microscopy (SAM) analysis on a Syrian bronze of the early I millennium BC. The objective was to derive a picture of modifications of the object's surface composition, induced by chemical attack by the ambient. Understanding degradation of ancient materials dating from a well-defined historical context provides information about long-term corrosion phenomena that is not possible from laboratory data. Such information is also useful for restoration and conservation efforts. While corrosion processes in the bulk are understood, this is not true for localized intergranular and transgranular surface corrosion in these materials. This requires information about local chemical composition and movement of ionic species that has not generally been available, and we find AES useful in accomplishing this task. SAM images of Cu, Sn and O, ~ 100-nm spatial resolution, and Auger point spectra show that Sn acts as a barrier against O₂ attack, as it entirely traps this gas into a SnO₂-like oxide, thus minimizing copper oxidation. Sub-micron spectromicroscopic evidence is given that S-induced corrosion occurs mainly via chemical attack along grain boundaries, where Sn has a low abundance and copper sulfides are detected. Lateral segregation of Sn and Cu domains is imaged with a spatial resolution of 15 nm. This result marks the best spatial resolution any analytical method has yet achieved in highlighting lateral chemical heterogeneities of ancient bronzes. Although archaeomaterials lie outside the mainstream applications of Auger techniques, this study provides convincing evidence that SAM can greatly advance our understanding of these materials.
11:00 AM		MC-TuM-9 Practical Applications of Surface Analysis Techniques in Electroplating C. Xu, J.A. Abys (Lucent Technologies) Electroplating has been widely used to deposit thin metal films on various substrates either to achieve certain functionality (wear resistance, solderability, wire bondability, corrosion resistance) or specific appearance. The materials properties are critical to the functionality and are dependent on the electroplating process. These properties are determined by the elemental, and chemical composition, and deposit structure. Surface analysis techniques are unique in their ability to provide specific diagnostic tools to study electrodeposited films. In this paper, the potential of various surface analysis techniques for investigating failure modes and new products development in electroplating industries will be discussed and demonstrated using various case studies. A comparison of techniques such as AES and XPS to traditional failure mode analysis methods such as Scanning Electron Microscopy (SEM) will be made.
11:20 AM		MC-TuM-10 Surface Chemistry and Physical Properties Related to Adhesion of Various Soldermask Materials C.A. Bradbury, Y. Du, T. Jiang (Micron Technology Inc.) In Flip Chip (FC) Ball Grid Array (BGA) packages, adhesion between soldermask material to mold compound, underfill and liquid encapsulant materials are critical to package reliability. Delamination will result in package crack and solder joint failure. In this study, the adhesion of several different types of soldermask materials to an underfill polymeric material was evaluated. The surface chemical properties of the soldermask materials were characterized using x-ray photoelectron spectroscopy (XPS) and surface tension test. The surface chemistry was correlated to the interfacial fracture toughness obtained by Mixed Mode Bending (MMB) test.