Journal of Vacuum Science and Technology最新文献

{"title":"X-ray spectroscopic identification of strain and structure-based resonances in a series of saturated carbon-cage molecules: Adamantane, twistane, octahedrane, and cubane","authors":"T. Willey, Jonathan R. I. Lee, D. Brehmer, O. A. P. Mellone, L. Landt, P. Schreiner, A. Fokin, B. Tkachenko, A. Meijere, S. Kozhushkov, A. V. Buuren","doi":"10.1116/6.0001150","DOIUrl":"https://doi.org/10.1116/6.0001150","url":null,"abstract":"Novel nanocarbons such as fullerenes, nanotubes, graphene, and nanodiamond reside at the cutting edge of nanoscience and technology. Along with chemical functionalization, geometric constraints (such as extreme curvature in nanotubes or defects within or at the surfaces of diamond nanoparticles) significantly alter the electronic states of the nanocarbon material. Understanding the effects of steric strain on the electronic structure is critical to developing nanoelectronic applications based on these materials. This paper presents a fundamental study of how strain affects the electronic structure in a benchmark series of some fundamental saturated carbon cage compounds. Adamantane, C10H16, the smallest diamondoid and arguably the smallest nanodiamond crystallite, has carbon atoms essentially commensurate with diamond lattice positions and possesses by far the least molecular strain of this series. Twistane also is a C10H16 isomer but the fixed cyclohexane twist conformation of the central ring introduces additional strain into the cage. Octahedrane [(CH)12] and cubane [(CH)8] are considerably more strained, culminating in cubane where carbon–carbon bonds lie either parallel or orthogonal to one another. Using gas-phase near-edge x-ray absorption fine structure spectroscopy to probe the unoccupied electronic states, we observe two major progressions across this series. First, a broad C–C σ* resonance in the absorption splits into two more narrow and intense resonances with increasing strain. Second, the first manifold of states previously associated with tertiary C–H σ* in the diamondoid series appears to broaden and shift to lower energy. This feature is more than twice as intense in cubane than in octahedrane, even though these two molecules have only tertiary carbons, with the chemical formula (CH)x. The spectral differences are entirely due to the shape of the molecules; in particular, in cubane, the features arise from a high degree of p-p interaction between parallel C–C bonds. In contrast to the conventional wisdom that near-edge x-ray absorption is primarily an atomically localized spectroscopy, molecular shape and associated strain lead to the dominant features in spectra acquired from this fundamental series of carbon cage structures.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89114316","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":"Direct-simulation Monte Carlo modeling of reactor-scale gas-dynamic phenomena in a multiwafer atomic-layer deposition batch reactor","authors":"Sudharshanaraj Thiruppathiraj, S. Ryu, Jiho Uh, L. Raja","doi":"10.1116/6.0000993","DOIUrl":"https://doi.org/10.1116/6.0000993","url":null,"abstract":"Atomic layer deposition (ALD) using multiwafer batch reactors has now emerged as the manufacturing process of choice for modern microelectronics at a massive scale. Stringent process requirements of thin film deposition uniformity within wafer (WiW) and wafer–wafer (WTW) in the batch, film conformity along submicrometer wafer features, thin film quality, and the utilization of expensive precursors in the reactor dictate ALD reactor design and process parameter optimization. This paper discusses a particle-based direct-simulation Monte Carlo (DSMC) of the full reactor scale simulation that overcomes the low Knudsen number limitation of typical continuum computational fluid dynamics approaches used for modeling low-pressure ALD reactors. A representative industrial multiwafer batch reactor used for the deposition of Si-based thin films with N2 and Si2Cl6 (hexachlorodisilane) as process feed gases with pressures in the range 43–130 Pa and a uniform reactor temperature of 600 °C is simulated. The model provides detailed insights into the flow physics associated with the transport of the precursor species from the inlets, through wafer feed nozzles, into the interwafer regions, and finally through the outlet. The reactor operating conditions are shown to be in the slip/transitional flow regime for much of the reactor volume and especially the feed gas nozzle and interwafer regions (where the Knudsen number approaches ∼0.2), justifying the need for a high-Knudsen number DSMC approach as in this work. For the simulated conditions, the nonuniformity of precursor species immediately above the wafer surface is predicted to be within <1% for a given wafer and <2% across the entire multiwafer stack. Results indicate that higher pressure degrades WiW and WTW uniformity. A reactor flow efficiency is defined and found to be ∼99%, irrespective of the chamber pressure.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87219860","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":"Observations of the Ag(3 × 1) phase on Ge(111)","authors":"C. Mullet, A. Rosen, S. Chiang","doi":"10.1116/6.0001183","DOIUrl":"https://doi.org/10.1116/6.0001183","url":null,"abstract":"Low-energy electron diffraction and low-energy electron microscopy were used to study the (3 × 1) phase of Ag on Ge(111) for temperatures less than 540 °C. This phase was observed when depositing 0.05–0.1 ML Ag at 370 °C. The ( 3×3)R30o phase formed when depositing 0.3 ML Ag at 170 °C, and then annealing to 200−360 °C resulted in a nonreversible phase transition to [(4 × 4) + (3 × 1)] phases at 360 °C. The 3 phase appears to be metastable for temperatures <250 °C since subsequent cooling did not cause it to reappear. These experimental observations suggest modifications to a published phase diagram for Ag/Ge(111).","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81983434","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":"Nonadiabatic localization of H2 in the field of two external positive tip charges","authors":"W. Schattke, M. Hove, R. D. Muiño","doi":"10.1116/6.0001138","DOIUrl":"https://doi.org/10.1116/6.0001138","url":null,"abstract":"For two external spherical tips with equal positive charges, the ground state of a hydrogen molecule is variationally determined within the quantum Monte Carlo scheme. For finiteness, the system is enclosed in a spherical container with randomly reflecting unstructured walls. The 12-dimensional system of two protons and two electrons is investigated ab initio without any adiabatic restrictions. We focus on the hydrogen center of mass (COM) distribution in continuation of previous work on ground state and vibration modes at a COM that was fixed in space. Our general purpose is to control the molecule’s position and orientation by external means, such as by two charged tips. To this end, knowledge is needed in order to find specific COM regions with a desired molecular orientation in the container at significant probability density of the molecule.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77753612","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":"Epitaxial film growth by thermal laser evaporation","authors":"Dong Yeong Kim, J. Mannhart, W. Braun","doi":"10.1116/6.0001177","DOIUrl":"https://doi.org/10.1116/6.0001177","url":null,"abstract":"We demonstrate the epitaxial growth of thin films by thermal laser evaporation. Epitaxial metal oxide films are grown by laser evaporating Ni, V, and Ru elemental sources in a variety of oxygen-ozone atmospheres on laser-heated oxide substrates. This results in NiO (111), VO2 (M1) (020), and RuO2 (110) epitaxial films on Al2O3 (0001) or MgO (100) substrates. The films show well-defined crystallographic orientation relationships with the substrates, as confirmed by in-plane and out-of-plane x-ray measurements. The results reveal the potential of thermal laser epitaxy for the epitaxial growth of ultrahigh-purity oxide heterostructures.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76308366","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":"Temperature dependent performance of ITO Schottky contacts on β-Ga2O3","authors":"Xinyi Xia, M. Xian, Chaker Fares, F. Ren, M. Tadjer, S. Pearton","doi":"10.1116/6.0001211","DOIUrl":"https://doi.org/10.1116/6.0001211","url":null,"abstract":"Sputtered indium tin oxide (ITO) was used as a rectifying contact on lightly n-type (n ∼ 1016 cm−3) β-Ga2O3 and found to exhibit excellent Schottky characteristics up to 500 K, with no thermally driven degradation to this temperature. The barrier height extracted from current–voltage characteristics was 1.15 ± 0.04 eV at 300 K and 0.78 ± 0.03 eV at 500 K, with thermionic behavior of charge carriers over the image force lowered Schottky barriers dominating the carrier transport at low temperatures. The breakdown voltages were 246, 185, and 144 V at 300, 400 and 500 K, respectively. At 600 K, the diodes suffered irreversible thermal damage. The diode on/off ratio was >105 for reverse biases up to 100 V. At higher reverse voltage, the current shows an I ∝ Vn relationship with voltage, indicating a trap-assisted space-charge-limited conduction (SCLC) mechanism. We observed this SCLC relation when the reverse voltage was larger than 100 V for 300 and 400 K and at <100 V at 500 K. The ITO can also be used to make Ohmic contacts on heavily doped Ga2O3 suggesting the possibility of completely optically transparent power devices.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80283017","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":"Plasma-enhanced atomic layer deposition of SiO2 film using capacitively coupled Ar/O2 plasmas: A computational investigation","authors":"Chenhui Qu, Y. Sakiyama, P. Agarwal, M. Kushner","doi":"10.1116/6.0001121","DOIUrl":"https://doi.org/10.1116/6.0001121","url":null,"abstract":"Plasma-enhanced atomic layer deposition (PE-ALD) is widely used for dielectric deposition in semiconductor fabrication due to its ability to operate at low temperatures while having high precision control. The PE-ALD process consists of two subcycles: precursor dosing and plasma exposure with gas purging and filling in between. In the PE-ALD of SiO2, a Si-containing precursor is first deposited on the surface, usually in a plasma-free environment. The surface is then exposed to an oxygen-containing plasma during which the residual components of the precursor are removed and the Si oxidized. Various factors affect the outcome of SiO2 PE-ALD, such as exposure times during each step, steric hindrance of the Si precursor, and plasma properties, such as the energy of ions incident onto the film. The results from computational investigations of the first layers of SiO2 PE-ALD at both reactor (cm) and feature (nm) scales are discussed in this paper. The example system uses bis(tertiary-butylamino)silane, SiH2[NH(C4H9)]2 as the silicon precursor during dosing and plasmas operating in Ar/O2 gas mixtures during the oxidation step. Parametric studies were performed for blanket deposition, as well as deposition in trenches and vias while varying power, pressure, plasma exposure time, aspect ratio, and ligand retention in the film. The general trends show that conditions that reduce the fluence of reactive oxygen species typically decrease the O/Si ratio, increase the vacancies in the films, and decrease the order of the film. Conditions that result in higher ion fluxes having higher energies produce the same result due to sputtering. The retention of ligand groups from the precursor significantly decreased growth rates while increasing vacancies and reducing the O/Si ratio.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89411897","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":"Cinnamaldehyde adsorption and thermal decomposition on copper surfacesa)","authors":"Bo Chen, R. Ponce, J. Guerrero‐Sanchez, N. Takeuchi, F. Zaera","doi":"10.1116/6.0001192","DOIUrl":"https://doi.org/10.1116/6.0001192","url":null,"abstract":"The uptake and thermal chemistry of cinnamaldehyde on Cu(110) single-crystal surfaces were characterized by temperature-programmed desorption and x-ray photoelectron spectroscopy (XPS). Adsorption at 85 K appears to be initiated by low-temperature decomposition to form styrene, which desorbs at 190 K, followed by the sequential buildup of a molecular monolayer and then a condensed molecular film. Molecular desorption from the monolayer occurs at 410 K, corresponding to a desorption energy of approximately 98 kJ/mol, and further decomposition to produce styrene (again) and other fragmentation products is seen at 550 K. The molecular nature and the quantitation of the low-temperature uptake were corroborated by the XPS data, which also provided hints about the adsorption geometry adopted by the unsaturated aldehyde on the surface. Density functional theory calculations, used to estimate adsorption energies as a function of coverage and coordination mode, pointed to possible η1-O binding, at least at high coverages, and to a stabilizing effect on the surface by the aromatic ring of cinnamaldehyde. Finally, coadsorption of oxygen on the surface was found to weaken the binding of cinnamaldehyde to the Cu substrate at high coverages without enhancing its uptake, but to not modify the decomposition mechanism or energetics in any significant way.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79110590","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":"Depth profile reconstruction of YCrO3/CaMnO3 superlattices by near total reflection hard x-ray photoelectron spectroscopy","authors":"Léo Cambou, Jin Hong Lee, M. Bibes, A. Gloter, J. Rueff","doi":"10.1116/6.0001113","DOIUrl":"https://doi.org/10.1116/6.0001113","url":null,"abstract":"We have determined the depth profile of YCrO3/CaMnO3 superlattices by hard x-ray photoemission spectroscopy in near total reflection conditions. YCrO3/CaMnO3 is prone to exhibit interesting magnetotransport properties owing to the large amount of electron transfer expected between Cr3+ and Mn4+. The depth profile was reconstructed by simulating the rocking curves of the different core levels using the YXRO software and fine-tuning the structural model. The results globally conform to scanning transmission electron microscopy and electron energy loss spectroscopy analysis, except for the top layer, whose structure and stoichiometry are found to be preserved in contrast to microscopy.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74886901","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":"Synthesis of model sodium sulfide films","authors":"R. McAuliffe, Victoria Petrova, M. McDermott, J. Tyler, Ethan C. Self, K. Persson, Ping Liu, G. Veith","doi":"10.1116/6.0001069","DOIUrl":"https://doi.org/10.1116/6.0001069","url":null,"abstract":"We report the direct deposition of model sodium sulfide films by RF magnetron sputtering from Na2S and Na2S2 deposition targets. Analytical characterization and electrochemical cycling indicate that the deposited films are amorphous with stoichiometries that correspond to Na2S3 and Na2S2 formed from the Na2S and Na2S2 targets, respectively. We propose that the loss of Na in the case of the Na2S target is due to preferential sputtering of Na resulting from the higher energy required to break the Na–S bonds in Na2S. The development of thin film sodium sulfides opens a new route to understanding their fundamental properties, such as Na+ transport, conductivity, and reactivity.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81178208","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}