Journal of Vacuum Science & Technology A Vacuum Surfaces and Films (J VAC SCI TECHNOL A )

Publisher: American Vacuum Society; American Institute of Physics, American Vacuum Society


The Journal of Vacuum Science and Technology A is devoted to reports of original research, review articles, and Critical Review articles. JVST A will include topics such as applied surface science, electronic materials and processing, fusion technology, plasma technology, surface science, thin films, vacuum metallurgy, and vacuum technology. It will contain the program and papers from the AVS National Symposium as well as the papers from other conferences and symposia sponsored by the AVS and its Divisions. JVST A is published six times annually.

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  • Other titles
    Journal of vacuum science & technology. A. Vacuum, surfaces, and films, JVST A, Journal of vacuum science and technology., Vacuum, surfaces, and films
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    Periodical, Internet resource
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    Journal / Magazine / Newspaper, Internet Resource

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American Vacuum Society

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    • On a public eprint server
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    • If funding agency rules apply, authors may post articles in PubMed Central 12 months after publication
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Publications in this journal

  • [show abstract] [hide abstract]
    ABSTRACT: A closed ion source (CIS) has been optimized by investigating the effect of electron entrance slit size and the effect of mesh in the slit. A stainless steel mesh was placed on the electron entrance slits for a uniform potential distribution inside the CIS anode. Sensitivity of the closed ion sources having four different slit sizes with and without the mesh was compared using mass spectra of SF6 gas (97% He gas base) introduced into the CIS anode through a needle valve. For each CIS, isolation of anode potential with a mesh in the slit exhibited a significant sensitivity enhancement, but ion current measured directly behind each CIS showed negligible mesh effect. In order to elucidate the mesh effect, electron trajectories were simulated inside the anode. The computer simulation shows that, with mesh in the slit, more electrons are focused to a central region of the anode. This suggests ions generated in the CIS with mesh should have higher probability of passing through the quadrupole mass filter.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 03/2014; 32(20):021603.
  • [show abstract] [hide abstract]
    ABSTRACT: The authors report on Langmuir probe measurements that show that hydrocarbon surfaces in contact with Ar plasma cause changes of electron energy distribution functions due to the flux of hydrogen and carbon atoms released by the surfaces. The authors compare the impact on plasma properties of hydrocarbon species gasified from an etching hydrocarbon surface with injection of gaseous hydrocarbons into Ar plasma. They find that both kinds of hydrocarbon injections decrease electron density and slightly increase electron temperatures of low pressure Ar plasma. For low percentages of impurities (∼1% impurity in Ar plasma explored here), surface-derived hydrocarbon species and gas phase injected hydrocarbon molecules cause similar changes of plasma properties for the same number of hydrocarbon molecules injected into Ar with a decrease in electron density of ∼4%.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 02/2014; 32(3):030601.
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    ABSTRACT: The material composition and the Si surface passivation of aluminum oxide (Al2O3) films prepared by atomic layer deposition using Al(CH3)3 and O3 as precursors were investigated for deposition temperatures (TDep) between 200 °C and 500 °C. The growth per cycle decreased with increasing deposition temperature due to a lower Al deposition rate. In contrast the material composition was hardly affected except for the hydrogen concentration, which decreased from [H] = 3 at. % at 200 °C to [H] < 0.5 at. % at 400 °C and 500 °C. The surface passivation performance was investigated after annealing at 300 °C–450 °C and also after firing steps in the typical temperature range of 800 °C–925 °C. A similar high level of the surface passivation performance, i.e., surface recombination velocity values <10 cm/s, was obtained after annealing and firing. Investigations of Al2O3/SiNx stacks complemented the work and revealed similar levels of surface passivation as single-layer Al2O3 films, both for the chemical and field-effect passivation. The fixed charge density in the Al2O3/SiNx stacks, reflecting the field-effect passivation, was reduced by one order of magnitude from 3·1012 cm−2 to 3·1011 cm−2 when TDep was increased from 300 °C to 500 °C. The level of the chemical passivation changed as well, but the total level of the surface passivation was hardly affected by the value of TDep. When firing films prepared at of low TDep, blistering of the films occurred and this strongly reduced the surface passivation. These resu- ts presented in this work demonstrate that a high level of surface passivation can be achieved for Al2O3-based films and stacks over a wide range of conditions when the combination of deposition temperature and annealing or firing temperature is carefully chosen.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(1):01A128 - 01A128-7.
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    ABSTRACT: Tantalum (Ta) oxides and their coatings have been proved to increase their applications in the biomedical fields by improving osseointegration and wear resistance. In this study, Ta oxide coatings containing different proportions of Ag are deposited on SS304 materials. A twin-gun magnetron sputtering system is used to deposit the tantalum oxide-Ag coating. In this study, Staphylococcus aureus, which exhibits physiological commensalism on the human skin, nares, and mucosal and oral areas, is chosen as the model for in vitro antibacterial analyses via a fluorescence staining method using Syto9. The cytocompatibility and adhesive morphology of human skin fibroblast cells (CCD-966SK) on the coatings are also determined by using the microculture tetrazolium assay. This study shows that Ta2O5 and Ta2O5-Ag coatings with 12.5 at. % of Ag exhibit improved antibacterial effects against S. aureus and have good skin fibroblast cell cellular biocompatibility.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(2):02B117-02B117-6.
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    ABSTRACT: A combination of the atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques is successfully employed to fabricate thin films incorporating superlattice structures that consist of single layers of organic molecules between thicker layers of ZnO. Diethyl zinc and water are used as precursors for the deposition of ZnO by ALD, while three different organic precursors are investigated for the MLD part: hydroquinone, 4-aminophenol and 4,4′-oxydianiline. The successful superlattice formation with all the organic precursors is verified through x-ray reflectivity studies. The effects of the interspersed organic layers/superlattice structure on the electrical and thermoelectric properties of ZnO are investigated through resistivity and Seebeck coefficient measurements at room temperature. The results suggest an increase in carrier concentration for small concentrations of organic layers, while higher concentrations seem to lead to rather large reductions in carrier concentration.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(1):01A105-01A105-5.
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    ABSTRACT: In this paper, a 20-nm SiOx thin film was deposited on a Pt/Ti/SiO2/Si substrate using radio-frequency magnetron sputtering. A Cu top electrode was deposited to form a Cu/SiOx/Pt device. The device was reversibly switched between a low-resistance state and a high-resistance state using DC voltage sweeping. Because of its bipolar switching behavior and the device structure, the switching mechanism can be explained by the formation and rupture of Cu filaments within the SiOx layer. An Argon (Ar) plasma treatment was used to modify the SiOx layer, which stabilized the resistive switching and, thus, improved the switching dispersion. The Ar plasma treatment caused ion bombardment, which increased the Cu diffusion coefficient within the SiOx layer, thus decreasing the operating voltage. In addition, various level of bombardment within the SiOx film caused partial damage of the SiOx film, which influenced the switching dispersion. The Ar-treated device in the 20-s plasma treatment demonstrated favorable memory properties, including a long retention time, nondestructive readout, and high resistance ratio, indicating that it could be viably applied in next-generation nonvolatile memory devices.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(2):02B111-02B111-5.
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    ABSTRACT: The authors report the growth and mechanical properties of epitaxial B1 NaCl-structure V1−xWxN/MgO(001) thin films with 0 ≤ x ≤ 0.60. The Gibbs free energy of mixing, calculated using density functional theory (DFT), reveals that cubic V1−xWxN solid solutions with 0 ≤ x ≲ 0.7 are stable against spinodal decomposition and separation into the equilibrium cubic-VN and hexagonal-WN binary phases. The authors show experimentally that alloying VN with WN leads to a monotonic increase in relaxed lattice parameters, enhanced nanoindentation hardnesses, and reduced elastic moduli. Calculated V1−xWxN lattice parameters and elastic moduli (obtained from calculated C11, C12, and C44 elastic constants) are in good agreement with experimental results. The observed increase in alloy hardness, with a corresponding decrease in the elastic modulus at higher x values, combined with DFT-calculated decreases in shear to bulk moduli ratios, and increased Cauchy pressures (C12–C44) with increasing x reveal a trend toward increased toughness.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(3):030603-030603-5.
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    ABSTRACT: The discharge characteristics in high power pulsed plasma enhanced chemical vapor deposition is studied with the aim to characterize the impact of high power pulses (HiPP). Using a power scheme of combined HiPP and direct current (DC) to ignite the plasma discharge, and adjusting the HiPP/DC time-averaged power ratio while keeping the total power constant, the effect of the high power pulses was isolated from the total power. By monitoring the discharge current along with the optical emission from the plasma, it is found that the amount of available ions increased with increasing HiPP/DC ratio, which indicates a higher plasma density. Using carbon films deposited from acetylene in an argon plasma as model system, a strong increase in deposition rate with higher HiPP/DC is observed. The increased deposition rate is ascribed to a more efficient plasma chemistry generated by the denser plasma.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(3):030602-030602-5.
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    ABSTRACT: FePt encapsulated carbon nanotubes (CNTs) were grown by thermal chemical vapor deposition using an Fe/Pt bilayer catalyst. The CNTs were grown according to the base growth model. Selected area electron diffraction results revealed that the encapsulated particles were A1-FePt, L10-FePt, and Fe3PtC. The crystal structures of particles found at the root parts of CNTs were not able to be identified, however. The layered structure of catalytic films seemed to be responsible for the difference in Pt content between particles found at tip and root parts of CNTs. Approximately 60% of CNTs grown at 800 °C had particles at their tip parts, compared to only 30% when the growth temperature was 700 °C, indicating that higher process temperatures promote particle encapsulation in CNTs.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(2):02B114-02B114-5.
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    ABSTRACT: In this article, the authors investigate chemical mechanical planarization (CMP) of gold. Our experiments show that the oxidizer concentration, hardness of the adhesion layer, and surfactants added to stabilize the slurry are the main factors determining the outcome of the process. A combination of 30% H2O2 solution and an alumina based slurry in 1:3 volumetric ratio along with added sodium dodecyl sulfate and poly(vinyl pyrrolidone) was successfully used to pattern gold in a CMP Damascene process. After fabricating inlaid gold structures with CMP, the authors observed that pattern density, as opposed to feature size, is the major factor in determining the amount of metal thinning in inlaid features. 10 μm lines at 5% density were thinned down by 40 nm, while 150 μm pads at 75% density were recessed by 20 nm. The authors believe that in this process, metal recess, that is a chemical effect, outweighs dishing, a feature-size dependent factor, in controlling the severity of metal thinning.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(2):021402-021402-5.
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    ABSTRACT: ZnO/Cr/ZnO trilayer films sandwiched with Pt electrodes were prepared for nonvolatile resistive memory applications. The threshold voltage of a ZnO device embedded with a 3-nm Cr interlayer was approximately 50% lower than that of a ZnO monolayer device. This study investigated threshold voltage as a function of Cr thickness. Both the ZnO monolayer device and the Cr-embedded ZnO device structures exhibited resistance switching under electrical bias both before and after rapid thermal annealing (RTA) treatment, but resistive switching effects in the two cases exhibited distinct characteristics. Compared with the as-fabricated device, the memory cell after RTA demonstrated remarkable device parameter improvements, including a lower threshold voltage, a lower write current, and a higher Roff/Ron ratio. Both transmission electron microscope observations and Auger electron spectroscopy revealed that the Cr charge trapping layer in Cr-embedded ZnO dispersed uniformly into the storage medium after RTA, and x-ray diffraction and x-ray photoelectron spectroscopy analyses demonstrated that the Cr atoms lost electrons to become Cr3+ ions after dispersion. These results indicated that the altered status of Cr in ZnO/Cr/ZnO trilayer films during RTA treatment was responsible for the switching mechanism transition.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(2):02B119-02B119-5.
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    ABSTRACT: The impact of the O2 content in SF6-O2 gas mixtures on the etch rate and sidewall profile of silicon (Si), germanium (Ge), and phosphorous doped germanium (Ge:P) in reactive ion etching has been studied. The characteristics of etch rate and sidewall profile are greatly affected by the O2 content. Below 50% of O2 content, a large variation in Ge etch rates is found compared to that of Si, but for O2 content above 50% the etch rates follow relatively the same trend. Lightly doped Ge shows the highest etch rate at a O2 concentration up to 20%. Sidewall angles range from a minimum of 80° to a maximum of 166°, with O2 concentration of 20% yielding perfect anisotropic mesa etch. Also at this O2 concentration, reasonable Si/Ge selectivity is possible. These observations indicate that by adjusting the O2 concentration, precision plasma etching of Si, Ge, and Ge:P is possible.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(3):031302-031302-5.
  • [show abstract] [hide abstract]
    ABSTRACT: In this work, AlNxOy thin films were deposited by reactive magnetron sputtering, using an aluminum target and an Ar/(N2+O2) atmosphere. The direct current magnetron discharge parameters during the deposition process were investigated by optical emission spectroscopy and a plasma floating probe was used. The discharge voltage, the electron temperature, the ion flux, and the optical emission lines were recorded for different reactive gas flows, near the target and close to the substrate. This information was correlated with the structural features of the deposits as a first step in the development of a system to control the structure and properties of the films during reactive magnetron sputtering. As the target becomes poisoned, the discharge voltage suffers an important variation, due to the modification of the secondary electron emission coefficient of the target, which is also supported by the evolution of the electron temperature and ion flux to the target. The sputtering yield of the target was also affected, leading to a reduction of the amount of Al atoms arriving to the substrate, according to optical emission spectroscopy results for Al emission line intensity. This behavior, together with the increase of nonmetallic elements in the films, allowed obtaining different microstructures, over a wide range of compositions, which induced different electrical and optical responses of films.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(2):021307-021307-10.
  • [show abstract] [hide abstract]
    ABSTRACT: In this research, Al2O3 films were grown by remote plasma-enhanced atomic layer deposition using a nonpyrophoric precursor, dimethylaluminum isopropoxide (DMAI), and oxygen plasma. After optimization, the growth rate was determined to be ∼1.5 Å/cycle within a growth window of 25–220 °C; the higher growth rate than reported for thermal atomic layer deposition was ascribed to the higher reactivity of the plasma species compared with H2O and the adsorption of active oxygen at the surface, which was residual from the oxygen plasma exposure. Both effects enhance DMAI chemisorption and increase the saturation density. In addition, a longer oxygen plasma time was required at room temperature to complete the reaction and decrease the carbon contamination below the detection limit of x-ray photoemission spectroscopy. The properties of the subsequent Al2O3 films were measured for different temperatures. When deposited at 25 °C and 200 °C, the Al2O3 films demonstrated a single Al-O bonding state as measured by x-ray photoemission spectroscopy, a similar band gap of 6.8±0.2 eV as determined by energy loss spectroscopy, a similar index of refraction of 1.62±0.02 as determined by spectroscopic ellipsometry, and uniform growth with a similar surface roughness before and after growth as confirmed by atomic force microscopy. However, the room temperature deposited Al2O3 films had a lower mass density (2.7 g/cm3 compared with 3.0 g/cm3) and a higher atomic ratio of O to Al (2.1 compared with 1.6) as indicated by x-ray reflectivity and Rutherford backscattering spectroscopy, respectively.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(2):021514-021514-9.
  • Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(2):021501-021501-6.
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    ABSTRACT: Interface bonding between alumina and various metals is discussed from the viewpoint of chemical thermodynamics. A method to predict the interface bonding species at an alumina/metal interface under equilibrium conditions is proposed by using the concept of chemical equilibrium for interface termination. The originality of this method is in the way a simple estimation of the interface binding energy, which is generally applicable to most metals, is developed. The effectiveness of this method is confirmed by careful examination of the experimental results. Comparison of the predicted and experimentally observed interface terminations reveals that the proposed method agrees well with the reported results. The method uses only basic quantities of pure elements and the formation enthalpy of oxides. Therefore, it can be applied to most metals in the periodic table and is useful for screening materials in the quest to develop interfaces with particular functions.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2014; 32(2):021102-021102-8.

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