Journal of Vacuum Science and Technology最新文献

{"title":"Oxygen-induced surface reconstructions on curved Ag(111)","authors":"Marie E. Turano, L. Juurlink, Maxwell Z. Gillum, E. Jamka, G. Hildebrandt, Faith Lewis, D. R. Killelea","doi":"10.1116/6.0001167","DOIUrl":"https://doi.org/10.1116/6.0001167","url":null,"abstract":"The adsorption of oxygen and the resultant O-induced surface reconstructions are key components in heterogeneously catalyzed reactions on silver metal surfaces. O uptake and reconstructions on planar Ag(111) are well-characterized, and in this paper, we show that curved Ag(111) features similar O adsorption and reconstructions. Through a systematic scanning tunneling microscope study of a curved Ag(111) single crystal exposed to gas-phase atomic oxygen at a temperature of 525 K, we observed O a d and, upon higher coverages, saw p( 4 × 4) and p( 4 × 5 √ 3) reconstructions form on both the A-type and B-type steps. Exposures at low temperatures (< 500 K) resulted in the formation of subsurface oxygen and the appearance of a stripe pattern and amorphous phase on the surface. Upon heating, stable surface reconstructions were formed. Although the geometric arrangement of atoms along the steps were different, A-type and B-type steps formed the same reconstructions. In addition, the B-type steps also saw the formation of several different features atop the oxygen reconstructions.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86570386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical ellipsometry: A method for selecting a near-minimal infrared measurement set for β-gallium oxide","authors":"F. Urban, D. Barton, M. Schubert","doi":"10.1116/6.0001002","DOIUrl":"https://doi.org/10.1116/6.0001002","url":null,"abstract":"The objective of this work is to develop a method for defining, a priori, a set of minimum ellipsometry measurements that provide for a near-minimal data set (measurement set) sufficient for an analysis of optically anisotropic crystals with monoclinic symmetry with minimal prior knowledge. Example measurements are obtained by reflection from two differently oriented smooth, flat, anisotropic, monoclinic β-Ga2O3 crystals. A measurement may consist of any set of common type ellipsometry data such as selected sets of normalized Jones matrix elements or selected sets of normalized Mueller matrix elements measured at selected angles of incidence and/or rotation of the sample, also know as table rotation. The only prior knowledge used here is the crystallographic surface orientation. The four complex-valued permittivity parameters of the monoclinic symmetry crystal are then the object of interest and the only remaining unknown parameters. The motif for our investigation is the desire to better understand how to reduce measurement time for the otherwise extensive data acquisition considered necessary thus far to fully characterize low-symmetry anisotropic materials in substrates and semiconductor heterostructures. The near-minimal measurement set introduced here is then obtained by selection from a prior, larger data set. The larger data set thus far largely overdetermines the amount of necessary information. The first criterion is that there be sufficient intensity of the reflected light considering the p and s polarized reflections produced by p and s polarized incident light. The second criterion for inclusion is that the permittivity tensor is sensitive to measurement, that is, a significant change in a measurement set results in a significant change in the solution for permittivity. Finally, the near-minimal measurement set must result in solvable sets of equations. This is examined by computing the Jacobian of the system of equations for various sets of measurements in order to only keep measurements for which the condition of the Jacobian falls below the threshold for usability. We find that sets containing four measurements of on-diagonal Jones matrix elements alone, obtained across a wide spread of table rotations, provide most sensitive and intrinsically sufficient information to solve for the permittivity values. In summary, the scheme consists of determining the following measurement conditions: (1) reflections of high intensity to enable accurate measurements. (2) sensitivity to the unknown parameters, and (3) a solvable set of equations.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85746634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Role of hydrogen species in promoting photoluminescence from Eu3+-doped ZnO thin films via bandgap excitation","authors":"H. Akazawa","doi":"10.1116/6.0001141","DOIUrl":"https://doi.org/10.1116/6.0001141","url":null,"abstract":"We studied the role of hydrogen-containing species (OH and/or H) in promoting photoluminescence (PL) from 1 at. % Eu3+ ions doped in ZnO thin films. The hydrogen concentration in the films was systematically changed by varying the substrate temperature and the vapor pressure of H2O gas supplied during sputter deposition. The correlation between the PL spectra via bandgap excitation and the degree of oxidization/hydrogenation was investigated by x-ray diffraction and Fourier-transform infrared spectroscopy. Films deposited at room temperature under H2O partial pressures higher than 10−2 Pa were sufficiently hydroxylated, as confirmed by the appearance of diffractions peaks from Zn(OH)2 coexisting with ZnO(002). Eu3+ emissions were observed after post-annealing in a vacuum or O2 atmosphere. When the H2O pressure was lower than 10−2 Pa, the ZnO:Eu films were so oxygen-deficient as to exhibit a metallic character, which deactivated the Eu3+ emission. Deposition at temperatures above 200 °C reduced the OH and/or H species incorporated in the ZnO films and only a faint Eu3+ emission was observed. The H2O pressure under which a sharp Eu3+ emission could be obtained was between 1.0 and 2.5 × 10−2 Pa if subsequent post-annealing was done in a vacuum. For more oxidized films deposited at 3.5 × 10−2 Pa, reduction by post-annealing in an H2 atmosphere was effective to generate a sharp and intense Eu3+ emission signal through reduction and hydrogenation, confirming that a moderate oxidization/hydrogenation state is a necessary condition. Codoped hydrogen species will facilitate substituting Zn2+ sites with emission-active Eu3+ ions and stabilize them.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85259161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessment of the (010) β-Ga2O3 surface and substrate specification","authors":"M. Mastro, C. Eddy, M. Tadjer, J. Hite, Jihyun Kim, S. Pearton","doi":"10.1116/6.0000725","DOIUrl":"https://doi.org/10.1116/6.0000725","url":null,"abstract":"Recent breakthroughs in bulk crystal growth of the thermodynamically stable beta phase of gallium oxide (β-Ga2O3) have led to the commercialization of large-area β-Ga2O3 substrates with subsequent epitaxy on (010) substrates producing high-quality films. Still, metalorganic chemical vapor deposition, molecular beam epitaxy, and processing of the (010) β-Ga2O3 surface are known to form subnanometer-scale facets along the [001] direction as well as larger ridges with features perpendicular to the [001] direction. A density function theory calculation of the (010) surface shows an ordering of the surface as a subnanometer-scale feature along the [001] direction. Additionally, the general crystal structure of β-Ga2O3 is presented, and recommendations are presented for standardizing (010) substrates to account for and control the larger-scale ridge formation.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86307589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of oxygen partial pressure on properties of monoclinic Ga2O3 deposited on sapphire substrates","authors":"J. Freitas, J. Culbertson, N. Nepal, A. Mock, M. Tadjer, Zixuan Feng, Hongping Zhao","doi":"10.1116/6.0000851","DOIUrl":"https://doi.org/10.1116/6.0000851","url":null,"abstract":"Thin monoclinic Ga2O3 films were deposited on c-plane sapphire substrates by low pressure chemical vapor deposition. The thin films were synthesized using high purity metallic gallium (Ga) and oxygen gas (O2) as precursors. The effect of oxygen volume percentage on the growth rate of thin films was observed at two growth temperatures. Within the investigated growth window, a maximum growth rate of ∼2.9 μm/h was obtained for an oxygen volume percentage of 4.8% with a growth temperature at 800 °C. The film growth rate decreased as growth temperature increased when other growth parameters were kept the same. X-ray diffraction indicates that all films have the β-Ga2O3 structure with (−201) orientation, and those deposited with higher oxygen partial pressure are thicker and have improved crystalline quality. Polarized micro-Raman scattering is consistent with small grains of (−201) β-Ga2O3 having random in-plane orientations. The large variation of the relative intensities of overlapping emission bands contributing to the broad luminescence emission extending between 1.5 and 4.5 eV (∼825 and 275 nm) suggest that deposition conditions strongly affect different defect concentrations. Films deposited at 800 °C with a higher oxygen partial pressure yielded higher resistance, which may result from the incorporation of gallium vacancies, identified as a compensating point defect affecting the electrical conductivity of bulk monoclinic Ga2O3.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91213640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low temperature Topographically Selective Deposition by Plasma Enhanced Atomic Layer Deposition with ion bombardment assistance","authors":"Taguhi Yeghoyan, V. Pesce, Moustapha Jaffal, G. Lefévre, R. Gassilloud, N. Possémé, M. Bonvalot, C. Vallée","doi":"10.1116/6.0000649","DOIUrl":"https://doi.org/10.1116/6.0000649","url":null,"abstract":"Area selective deposition via atomic layer deposition (ALD) has proven its utility in elementary nanopatterning processes. In the case of complex 3D patterned substrates, selective deposition processes lead to vertical sidewall coverage only, or top and bottom horizontal surface coverage only, to enable advanced nanopatterning and further miniaturization of microelectronic devices. While many fabrication strategies for vertical only Topographically Selective Deposition (TSD) have already been developed, the horizontal TSD case needs further attention. In this work, we propose a versatile route for the TSD on 3D top and bottom horizontal surfaces along with a proof-of-concept for such selective Ta2O5 thin film deposition. The strategy at stake relies on a plasma enhanced atomic layer deposition process assisted by energetic ion bombardment during the plasma step and followed by a postgrowth wet etching step. The effectiveness of this strategy is based on a careful adjustment of processing temperatures purposely set at low temperature, most probably below the ALD temperature window. Anisotropic ion bombardment via substrate biasing during the plasma step provides an extra amount of thermal energy only to exposed horizontal surfaces, which in turn enables a selective densification of the thin film under growth. The difference in thin film density on horizontal and vertical surfaces enables the property-selective etching of vertical surfaces, generating horizontal TSD. A proof-of-concept for such low temperature TSD is shown in the case of 3D trenched substrates with an aspect ratio of 14.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86421658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of plasma power on deposition mechanism and structural properties of MoOx thin films by plasma enhanced atomic layer deposition","authors":"Chen Wang, Chun-Hui Bao, Wan‐Yu Wu, Chia‐Hsun Hsu, Ming-Jie Zhao, Shui‐Yang Lien, W. Zhu","doi":"10.1116/6.0000968","DOIUrl":"https://doi.org/10.1116/6.0000968","url":null,"abstract":"In this study, amorphous films of molybdenum oxide (MoOx) had been prepared by plasma enhanced atomic layer deposition (PEALD) technique using molybdenum hexacarbonyl (Mo(CO)6) as a metal precursor and the mixture gas of O2/Ar as reactants. The influence of plasma power from 1000–3000 W on PEALD-MoOx films’ structure properties was investigated, and the deposition mechanism was proposed. Based on the results, the plasma power playing a crucial role in depositing MoOx films is concluded. A maximum deposition rate of MoOx films is 0.76 A/cycle, which is achieved at the optimal plasma power of 2000 W owing to the enhancement of plasma radicals’ intensity. The Mo5+ and Mo6+ oxidation states that emerged in all the films were illustrated by x-ray photoelectron spectroscopy studies, which means oxygen deficiency in substoichiometric MoOx films. The proportion of no-lattice oxygen decreases first and then increases with the increase of the plasma power. A low power and a high power may lead to deficient oxidation and obvious ion bombardment effect, respectively, which lead to the reduction of MoOx film quality, as indicated by the refractive index, atomic force microscopy, and scanning electron microscopy. The clarification of the effect of plasma power on PEALD-MoOx thin films is greatly beneficial to the application in high performance electronic devices.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89219178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of anti-reflection coating on the performance of silicon solar cells with nanocrystalline quantum dots downshifting film","authors":"Ala H. Sabeeh, Alyssa N. Brigman, J. Ruzyllo","doi":"10.1116/6.0000833","DOIUrl":"https://doi.org/10.1116/6.0000833","url":null,"abstract":"This experiment explores the effect of lithium fluoride (LiF) antireflection coating (ARC) on the performance of commercial silicon solar cells with mist deposited nanocrystalline quantum dots (NQD) downshifting film. The effect of blanket deposited and patterned NQD and ARC films is investigated. Significant improvement of the performance of cells with ARC is observed. Specifically, 67% increase in the average external quantum efficiency of silicon solar cells covered with AR coating in the UV range of 300–400 nm is noted. The micropatterning of NQD/LiF films improves light trapping inside the cell and enhances power conversion efficiency (PCE) of the cell by 19.5%. Overall, this experiment demonstrates that the ARC formation on top of the mist deposited NQD downshifting film results in measurable improvement in the performance of the commercial silicon solar cells.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83624714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Atomic layer deposition and selective etching of ruthenium for area-selective deposition: Temperature dependence and supercycle design","authors":"M. Vos, Sonali N. Chopra, J. Ekerdt, S. Agarwal, W. Kessels, A. Mackus","doi":"10.1116/6.0000912","DOIUrl":"https://doi.org/10.1116/6.0000912","url":null,"abstract":"","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75383355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microstructure and optical properties of sputter-deposited Ga2O3 films","authors":"Eduardo Vega, S. Isukapati, T. Oder","doi":"10.1116/6.0000938","DOIUrl":"https://doi.org/10.1116/6.0000938","url":null,"abstract":"","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74830727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}