Robert J. Purtell

Precision parts cleaning using supercritical fluids

Supercritical fluid extraction and chromatography measurements were made on pieces of disk drive actuator components in order to understand how to clean and analyse these parts. Extract analyses were made by Fourier transform infrared (FTIR) and flame ionization detector measurements. Hydrocarbons, silicones, and fluorocarbons were seen on various pieces of different samples using FTIR, time‐of‐flight static secondary‐ion mass spectrometry (TOF‐SSIMS), and x‐ray photoelectron spectroscopy. In addition TOF‐SSIMS detected di‐isooctyl phthalate. Silicones and di‐isooctyl phthalate could be removed by CO2 extraction.

Chemical reaction and silicide formation at the Pt/Si interface

Surface spectroscopy (UPS and AES) and transmission electron microscopy (TEM) techniques have been used to study the chemical behavior of interfaces formed by Pt deposition (∼0.1–100 A) on atomically clean Si(111) and Si(100) surfaces prepared by sputter/annealing. As shown by the annealing behavior of a thicker (∼100 A) overlayer, growth of an intermixed phase begins only at ∼200–300 °C and leads to formation of a product which is stable to 500 °C. TEM observations show this product to be single‐phase PtSi. The UPS spectrum for PtSi is dominated by two distinct peaks at −3.7 and −6.2 eV, while the Si L2,3VV AES spectrum also show features characteristic of silicidelike bonding. With annealing above ∼400 °C, excess Si segregates to the top surface of the PtSi overlayer. Upon 25 °C deposition, both UPS and AES show clear indications of strong Pt/Si intermixing across the interface from the submonolayer range to ∼40 A. In the low (submonolayer to few monolayer) coverage range at temperatures ≤300 °C, the ne...

The formation of the Schottky barrier at the V/Si interface

Synchrotron radiation photoemission measurements have been used to study the behavior of the Schottky barrier height φ bn and electronic structure of the V/Si interface for both cleaved Si(111)- (2X1) and sputter-cleaned Si(111)—(7 X 7) surfaces. Although the Schottky barrier height φ bn of the clean surface is influenced by surface reconstruction (and by steps), the barrier becomes pinned at low (~ 2 A) V coverage at a position essentially independent of the initial clean surface structure. Formation of the bulk V metal band structure is not complete until ∼ 30–40 A V coverage, indicating coverage-dependent structural effects in the growth of the metal film. These effects also seem to produce secondary influences on φ bn ,which are manifested as a gradual increase of φ bn ,with higher coverage or mild (~200°C) annealing. However, upon higher temperature annealing (>350°C) the trend reverses, with φ bn decreasing to a value (∼0.64 eV) characteristic of the bulk VSi2contact which is formed at 500–550 °C; this change in the behavior of φ bn is directly correlated with the onset of atomic mixing across the interface.

Schottky barrier formation at Pd, Pt, and Ni/Si(111) interfaces

Synchrotron radiation photoemission measurements have been used to study Schottky barrier formation and the electronic structure of interfaces of Si with Pt, Pd, and Ni. High resolution photoemission spectroscopy of the Si 2p core levels has been used to monitor changes in band bending (or Schottky barrier height) when the metal is deposited on the Si surface. Barrier height measurements on sputter‐cleaned (i.e., ion bombardment and subsequent annealing) and on heat‐cleaned (i.e., annealing only) samples show no effect of the ion bombardment on the rate of change in barrier height with coverage. The Schottky barrier height reaches a saturation value within 1 A metal coverage for Pt and Ni, but it requires ∼4.5 A for Pd. For the Ni/Si interface, measurements of the valence electronic structure indicate that the Schottky barrier height is unrelated to the existence of a metallic character of the contact.

Effect of TiOx nucleation layer on crystallization of Bi4Ti3O12 films

Abstract Crystalline Bi4Ti3O12 films were fabricated using a chemical solution deposition route. The spin solution was prepared with bismuth acetate and titanium isopropoxide dissolved in a mixture of acetic acid and 2-methoxyethanol. The effect of a titanium oxide buffer layer and Bi4Ti3O12 seed layers on Bi4Ti3O12 film crystallization was studied. The titanium oxide buffer layer and the Bi4Ti3O12 seed layer reduced grain size and grain size distribution. Less preferential c axis orientation was observed on TiOx than on Pt. Ferroelectric hysteresis loops were measured on Bi4Ti3O12 films with thickness’ ranging from 70 to 180 nm at 1–16 volts with remanent polarizations up to 14 μC/cm2. Remanent polarizations of 3–4 μC/cm2 at 4 volts were measured for Bi4Ti3O12 films on Pt with all the layers annealed all at once with no titanium oxide buffer layers or Bi4Ti3O12 seed layers.

Growth of bismuth titanate films by chemical vapor deposition and chemical solution deposition

Abstract Bismuth titanate, Bi4Ti3O12 (BIT) was grown via chemical vapor deposition (CVD) and chemical solution deposition (CSD). The BIT films were grown by CVD, with triphenylbismuth and titanium isopropoxide. BIT films were fabricated by CSD using a solution prepared with bismuth ethylhexanoate and titanium butoxyethoxide dissolved in butoxyethanol. What is readily apparent in both CVD and CSD BIT films, is that composition plays a dominant role in determining not only phase purity but texturing as well and that a small composition variation can lead to dramatic changes in phase purity, orientation and electrical properties. In the CVD BIT films composition was controlled by changing the growth temperature. In the CSD BIT films composition was controlled by changing the solution composition. CVD BIT films crystallized at lower temperatures with better crystallinity and greater c-axis texturing than the CSD BIT films at comparable Bi/Ti composition. For both CVD and CSD, titanium rich films contained a m...

Formation of the Schottky barrier at the Pd/Si interface☆

Abstract The formation of the Schottky barrier (SB) at the PdSi interface and its correlation to electronic and structural properties has been investigated. Experiments have been carried out using interfaces with thick and thin metal coverages. The thick contact experiment shows that the SBH Φ b is independent of the bulk silicide structure and that it can be established upon Pd deposition at room temperature. In the thin contact experiment, the use of a synchrotron radiation source and high-resolution photoemission spectroscopy makes possible simultaneous observations of variations in SBH and valence band spectra from a clean Si surface up to several monolayers of metal coverage. The SBH values from thin and thick-contacts establish the true interface character of Φ b . Valence spectra show that SBH can be established without a full development of the metallic character of the reacted overlayer. Combining these results, we conclude that the SBH for the PdSi interface is determined by the basic interaction between Pd and Si atoms at the interface prior to the development of a metallic band structure and a well-defined silicide phase in the overlayer.