The AlN incorporation probability in single crystal Hf1−xAlxN(001) layers is controllably adjusted between ∼0% and 100% by varying the ion energy (Ei) incident at the growing film over a narrow range, 10–40eV. The layers are grown on MgO(001) at 450°C using ultrahigh vacuum magnetically unbalanced reactive magnetron sputtering from a Hf0.7Al0.3 alloy target in a 5%-N2/Ar atmosphere at a total pressure of 20mTorr (2.67Pa). The ion to metal flux ratio incident at the growing film is constant at 8. Epitaxial film compositions vary from x=0.30 with Ei=10eV, to 0.27 with Ei=20eV, 0.17 with Ei=30eV, and ⩽0.002 with Ei⩾40eV. Thus, the AlN incorporation probability decreases by greater than two orders of magnitude. This extraordinary range in real-time manipulation of film chemistry during deposition is due to the efficient resputtering of deposited Al atoms (27 amu) by Ar+ ions (40 amu) neutralized and backscattered from heavy Hf atoms (178.5 amu) in the film. This provides a new reaction pathway to synthesize, at high deposition rates, compositionally complex heterostructures, multilayers, and superlattices with abrupt interfaces from a single alloy target by controllably switching Ei. For multilayer and superlattice structures, the choice of Ei value determines the layer composition and the switching periods control the individual layer thickness.

We describe the design of a tandem instrument combining a low-energy electron microscope (LEEM) and a negative ion accelerator. This instrument provides video rate imaging of surface microtopography and the dynamics of its evolution during irradiation by energetic ions, at temperatures up to 1700 K. The negative ion beam is incident on the sample at normal incidence with impact energies selectable in the range 0–5 keV, and with current densities up to 30 μA/cm2 (∼2×1014 ions/cm2 s or ∼0.2 ML/s). The LEEM operates at a base pressure in the 10−9 Pa range. We describe the design and operating principles of the instrument and present examples of Pt(1 1 1) and Si(0 0 1) self-ion irradiation experiments.

In cells containing Li(1.05)(Ni(1/3)Co(1/3)Mn(1/3))(0.95)O(2)-based positive and graphite-based negative electrodes, a significant portion of cell impedance rise on aging is known to be from the negative electrode. One possible reason for this impedance rise is the dissolution of transition-metal elements from the oxide electrode that accumulate and create a high-impedance layer at the negative electrode electrolyte interface. This article details dynamic secondary ion mass spectrometry (SIMS) measurements, which provide a relative comparison of Mn, Co, and Ni contents on fresh, formed, and aged graphite electrodes. The data clearly indicate that these transition-metal elements accumulate at the electrode surface and diffuse into the electrode during cell aging. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.2987680] All rights reserved.

The impedance rise that results from the accelerated aging of high-power lithium-ion cells containing LiNi0.8Co0.15Al0.05O2-based positive and graphite-based negative electrodes is dominated by contributions from the positive electrode. Data from various diagnostic experiments have indicated that a general degradation of the ionic pathway, apparently caused by surface film formation on the oxide particles, produces the positive electrode interface rise. One mechanistic hypothesis postulates that these surface films are components of the negative electrode solid electrolyte interphase (SEI) layer that migrate through the electrolyte and separator and subsequently coat the positive electrode. This hypothesis is examined in this article by subjecting cells with LiNi0.8Co0.15Al0.05O2-based positive and Li4/3Ti5/3O4-based negative electrodes to accelerated aging. The impedance rise in these cells was observed to be almost entirely from the positive electrode. Because reduction products are not expected on the 1.55V Li4/3Ti5/3O4 electrode, the positive electrode impedance cannot be attributed to the migration of SEI-type fragments from the negative electrode. It follows then that the impedance rise results from mechanisms that are “intrinsic” to the positive electrode.

The Advanced Technology Development (ATD) Program is a multilaboratory effort to assist industrial developers of high-power lithium-ion batteries overcome the barriers of cost, calendar life, abuse tolerance, and low-temperature performance so that this technology may be rendered practical for use in hybrid electric vehicles (HEVs). Included in the ATD Program is a comprehensive diagnostics effort conducted by researchers at Argonne National Laboratory (ANL), Brookhaven National Laboratory (BNL), and Lawrence Berkeley National Laboratory (LBNL). The goals of this effort are to identify and characterize processes that limit lithium-ion battery performance and calendar life, and ultimately to describe the specific mechanisms that cause performance degradation. This report is a compilation of the diagnostics effort conducted since spring 2001 to characterize Generation 2 ATD cells and cell components. The report is divided into a main body and appendices. Information on the diagnostic approach, details from individual diagnostic techniques, and details on the phenomenological model used to link the diagnostic data to the loss of 18650-cell electrochemical performance are included in the appendices. The main body of the report includes an overview of the 18650-cell test data, summarizes diagnostic data and modeling information contained in the appendices, and provides an assessment of the variousmore » mechanisms that have been postulated to explain performance degradation of the 18650 cells during accelerated aging. This report is intended to serve as a ready reference on ATD Generation 2 18650-cell performance and provide information on the tools for diagnostic examination and relevance of the acquired data. A comprehensive account of our experimental procedures and resulting data may be obtained by consulting the various references listed in the text. We hope that this report will serve as a roadmap for the diagnostic analyses of other lithium-ion technologies being evaluated for HEV applications. It is our hope that the information contained in this report will lead to the development of new lithium-ion cell chemistries and designs that will meet the 15-year cell calendar-life goal established by DOE's FreedomCar and Fuel Partnership.« less

Hybrid electric vehicles (HEV) need long-lived high-power batteries as energy storage devices. Batteries based on lithium-ion technology can meet the high-power goals but have been unable to meet HEV calendar-life requirements. As part of the US Department of Energy's Advanced Technology Development (ATD) Program, diagnostic studies are being conducted on 18650-type lithium-ion cells that were subjected to accelerated aging tests at temperatures ranging from 40 to 70 C. This article summarizes data obtained by gas chromatography, liquid chromatography, electron microscopy, X-ray spectroscopy and electrochemical techniques, and identifies cell components that are responsible for the observed impedance rise and power fade.

Hybrid electric vehicles (HEV) need long-lived high-power batteries as energy storage devices. Batteries based on lithium-ion technology can meet the high-power goals but have been unable to meet HEV calendar-life requirements. As part of the US Department of Energy’s Advanced Technology Development (ATD) Program, diagnostic studies are being conducted on 18650-type lithium-ion cells that were subjected to accelerated aging tests at temperatures ranging from 40 to 70°C. This article summarizes data obtained by gas chromatography, liquid chromatography, electron microscopy, X-ray spectroscopy and electrochemical techniques, and identifies cell components that are responsible for the observed impedance rise and power fade.

X-ray photoelectron (XPS), ultraviolet photoelectron (UPS), and Auger electron spectroscopy (AES) spectra are presented from epitaxial, single-crystal transition-metal (TM) nitride (ScN, TiN, VN, and CrN) layers, that were grown in situ in an ultrahigh-vacuum (UHV) magnetron sputter deposition system attached to the analysis chambers. The samples are near-stoichiometric with N/Me ratios determined by Rutherford backscattering spectroscopy (RBS), and contain no bulk or surface impurities detectable by XPS, AES, or RBS. The spectra therefore represent reliable reference data. We also present XPS and AES data from sputter-etched samples in order to quantitatively determine the effect of preferential sputtering of nitrogen in TM nitrides. The sputter etching was performed under conditions typical for sputter cleaning of air-exposed samples until a steady state N/Me ratio is reached.

A comparison of the effects of a variety of low power (<1W) plasmas (air, NH3 and N2) on highly ordered pyrolytic graphite (HOPG), polyacrylonitrile (PAN)-based and pitch based carbon fibres has been studied using X-ray photoelectron spectroscopy. Grazing angle techniques have been used to probe only the first 12–15 Å of the fibre surface. Plasma treatments were carried out in an in situ plasma cell which was attached to a PHI 5400 X-ray photoelectron spectrometer. This enabled the immediate effects of the plasma to be studied before the treated surface was exposed to air. The reactivity towards a particular plasma is shown to be largely dependent on the structure of the fibre surface. Air plasmas are much more reactive to the fibre surface than either nitrogen or ammonia plasma. Hydroxyl and carboxyl groups are detected on PAN based fibres where as only hydroxyl groups were detected on pitch based fibres and HOPG. Both ammonia and nitrogen plasmas were successful in introducing aliphatic and aromatic amines (C-NH2) together with small number of immines (-CNH). The number of CN groups produced on the higher modulus fibres was undesirably low. Their concentration was increased by biasing the fibres to a negative potential (10–30V) during plasma exposure. Examination of these treated fibre surfaces showed that little, if any, etching of the fibre surface had taken place and hence damage to the fibre was minimal.

The effect of a variety of low power plasma treatments (e.g., NH3, N2, air and Ar) on low modulus carbon fibre surfaces have been examined using X-ray photoelectron spectroscopy. Grazing angle techniques have been used to probe only the first 12–15A of the fibre surface. Plasma treatments were carried out in an in situ plasma cell which was attached to a PHI 5400 X-ray photoelectron spectrometer. This enabled the immediate effects of the plasma to be studied before the treated surface was exposed to air. Air plasmas introduced both alcohol and carboxyl groups onto the fibre surfaces. Nitrogen plasmas gave very similar results to ammonia plasmas with the formation of three nitrogen containing species on the fibre surface. The signal at 398.9eV was assigned to a combination of aromatic amines (-NH2), and -CNH groups. Its relative intensity, as expected was greater for fibres treated in ammonia plasmas. Air exposure of these activated surfaces results in a strongly bound -O-H layer. Significant etching or pitting was not observed in the scanning electron micrographs of these treated fibres. Comparing XPS spectra of the immediate surface with those taken at bulk sensitive angles, it can be concluded that chemical change only occurred in the first few atomic layers.

The effect of low power nitrogen and ammonia plasmas on carbon fibre surfaces has been studied using X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy (SEM). A comparison is made between two polyacrylonitrile based fibres and a pitch based fibre. Grazing angle techniques have been exploited to probe only the first 12-15A of the fibre surface. Plasma treatments were carried out in an insitu plasma treatment cell which was attached to a PHI 5400 X-ray photoelectron spectrometer enabling the immediate effects of the plasma to be studied before the treated surface was exposed to air.

A commercial sputtered neutral mass spectrometer, using a rf-generated plasma for both sputtering and postionization of sputtered particles, has been modified to improve sensitivity for trace analysis. The modified instrument has been used to depth profile zinc-implanted gallium arsenide. A detection limit of 20 ppma was attained for zinc under conditions of maximum depth resolution from an analyzed sample area of 0.2 cm2 with a useful yield of 5 to 7×10−10 . The results have been compared with those of secondary ion mass spectrometry. Sputtered neutral mass spectrometry (SNMS) depth profiles revealed zinc redistribution in one heavily implanted sample, leading to the discovery of unusual structural damage through transmission electron microscopy. This investigation is discussed as an example of the usefulness of the SNMS technique in practical applications.