Hofsäss, Hans Christian

[["dc.bibliographiccitation.artnumber","115410"],["dc.bibliographiccitation.issue","11"],["dc.bibliographiccitation.journal","PHYSICAL REVIEW B"],["dc.bibliographiccitation.volume","65"],["dc.contributor.author","Hofsass, H."],["dc.contributor.author","Feldermann, H."],["dc.contributor.author","Eyhusen, S."],["dc.contributor.author","Ronning, Carsten"],["dc.date.accessioned","2018-11-07T10:31:08Z"],["dc.date.available","2018-11-07T10:31:08Z"],["dc.date.issued","2002"],["dc.description.abstract","Boron nitride film growth from B and N ion deposition is studied. We observe growth of the cubic phase (c-BN) between 75 eV and 5 keV and a transition to sp(2)-bonded BN growth between 5 and 10 keV, as predicted by the cylindrical spike model. Atomic rearrangements in thermal spikes are identified as the mechanism responsible for c-BN formation and suppression of defect accumulation. The onset of defect accumulation eventually enhances the growth of sp(2)-bonded BN. The results highlight the fundamental role of the balance between thermal spikes and defect accumulation in ion deposition processes."],["dc.identifier.doi","10.1103/PhysRevB.65.115410"],["dc.identifier.isi","000174548400116"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/44033"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","American Physical Soc"],["dc.relation.issn","1098-0121"],["dc.title","Fundamental role of ion bombardment for the synthesis of cubic boron nitride films"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","art. no."],["dc.bibliographiccitation.journal","MRS INTERNET JOURNAL OF NITRIDE SEMICONDUCTOR RESEARCH"],["dc.bibliographiccitation.lastpage","W11.44"],["dc.bibliographiccitation.volume","5"],["dc.contributor.author","Ronning, Carsten"],["dc.contributor.author","Hofsass, H."],["dc.contributor.author","Stotzler, A."],["dc.contributor.author","Deicher, M."],["dc.contributor.author","Carlson, E. P."],["dc.contributor.author","Hartlieb, P. J."],["dc.contributor.author","Gehrke, T."],["dc.contributor.author","Rajagopal, P."],["dc.contributor.author","Davis, R. F."],["dc.date.accessioned","2018-11-07T11:11:57Z"],["dc.date.available","2018-11-07T11:11:57Z"],["dc.date.issued","2000"],["dc.description.abstract","Single crystalline (000l) gallium nitride layers, capped with a thin epitaxial aluminum nitride Laver, were implanted with magnesium and subsequently annealed in vacuum to 1150-1300 degreesC for 10-60 minutes. Photoluminescence (PL) measurements showed the typical donor acceptor pair (DAP) transition at 3.25 eV after annealing at high temperatures, which is related to optically active Mg accepters in GaN. After annealing at 1300 degreesC a high degree of optical activation of the implanted Mg atoms was reached in the case of low implantation doses. Electrical measurements, performed after removing the AlN-cap and the deposition of Pd/Au contacts, showed no p-type behavior of the GaN samples due to the compensation of the Mg accepters with native n-type defects."],["dc.identifier.isi","000090103600100"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/53551"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Materials Research Society"],["dc.publisher.place","Warrendale"],["dc.relation.conference","Symposium on GaN and Related Alloys Held at the MRS Fall Meeting"],["dc.relation.eventlocation","BOSTON, MASSACHUSETTS"],["dc.relation.issn","1092-5783"],["dc.title","Photoluminescence characterization of Mg implanted GaN"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1203"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Journal of Applied Physics"],["dc.bibliographiccitation.lastpage","1207"],["dc.bibliographiccitation.volume","93"],["dc.contributor.author","Gerhards, Inga"],["dc.contributor.author","Ronning, Carsten"],["dc.contributor.author","Hofsass, H."],["dc.contributor.author","Seibt, M."],["dc.contributor.author","Gibhardt, Holger"],["dc.date.accessioned","2018-11-07T10:41:39Z"],["dc.date.available","2018-11-07T10:41:39Z"],["dc.date.issued","2003"],["dc.description.abstract","Amorphous carbon thin films containing 0-50 at. % Cu have been grown by mass selected ion beam deposition in order to synthesize isolated Cu nanoparticles within a diamond-like matrix. Raman spectroscopy and x-ray photoelectron spectroscopy show that the sp(3) content of the matrix decreases with increasing Cu content. Simultaneously, the mean particle size of the embedded Cu nanocrystals increases, as x-ray diffraction and transmission electron microscopy analysis reveal. There is apparently no dependence of the matrix structure on the Cu+ ion energy, while the Cu content is strongly influenced by this deposition parameter. (C) 2003 American Institute of Physics."],["dc.identifier.doi","10.1063/1.1531211"],["dc.identifier.isi","000180134200065"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/46593"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Inst Physics"],["dc.relation.issn","0021-8979"],["dc.title","Ion beam synthesis of diamond-like carbon thin films containing copper nanocrystals"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1356"],["dc.bibliographiccitation.issue","8-9"],["dc.bibliographiccitation.journal","NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS"],["dc.bibliographiccitation.lastpage","1359"],["dc.bibliographiccitation.volume","267"],["dc.contributor.author","Zutz, Hayo"],["dc.contributor.author","Lyzwa, Dominika"],["dc.contributor.author","Ronning, Carsten"],["dc.contributor.author","Seibt, Michael"],["dc.contributor.author","Hofsaess, Hans"],["dc.date.accessioned","2018-11-07T08:30:31Z"],["dc.date.available","2018-11-07T08:30:31Z"],["dc.date.issued","2009"],["dc.description.abstract","The quasi-simultaneous deposition of low energy-mass-selected C+ and metal(+) ions leads to the formation of metal-carbon nanocomposites. In the case of C+ and Cu+ deposition, a homogeneous distribution of small copper clusters in an amorphous carbon matrix is expected. However, at a certain C+/Cu+ fluence ratio and energy range, alternately metal-rich and metal-deficient layers in an amorphous carbon matrix with periods in the nm range develop have been observed. The metal-rich layers consist of densely distributed crystalline Cu particles while the metal-deficient layers are amorphous and contain only few and small Cu clusters. The formation of multilayers can be described by an interplay of sputtering, surface segregation, ion induced diffusion, and the stability of small clusters against ion bombardment. This formation has been investigated for the a-C:Cu system with respect to the ion energy and the C+/Cu+ fluence ratio. The sputter coefficient S-M = r(f)S(CCu) + S-CuCu is the parameter to switch between layer growth (S-M < 1) and homogeneous cluster distribution (S-M > 1). (C) 2009 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.nimb.2009.01.046"],["dc.identifier.isi","000266519900037"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/16907"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.publisher.place","Amsterdam"],["dc.relation.conference","16th International Conference on Ion Beam Modification of Materials"],["dc.relation.eventlocation","Dresden, GERMANY"],["dc.relation.issn","0168-583X"],["dc.title","Self-organized formation of layered carbon-copper nanocomposite films by ion deposition"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","213"],["dc.bibliographiccitation.issue","1-3"],["dc.bibliographiccitation.journal","HYPERFINE INTERACTIONS"],["dc.bibliographiccitation.lastpage","216"],["dc.bibliographiccitation.volume","184"],["dc.contributor.author","Bharuth-Ram, K."],["dc.contributor.author","Hofsaess, H."],["dc.contributor.author","Ronning, Carsten"],["dc.date.accessioned","2018-11-07T11:14:31Z"],["dc.date.available","2018-11-07T11:14:31Z"],["dc.date.issued","2008"],["dc.description.abstract","The electric field gradients at Eu sites in GaN have been investigated in conversion electron Mossbauer spectroscopy (CEMS) in which Eu-151 probe ions were implanted into an undoped GaN layer grown on a sapphire substrate. The sample was implanted with 120 keV Eu-151 ions to a fluence of 1 x 10(15), and annealed at 1,200 K. CEMS spectra of the Eu-151 21.6 keV transition were collected, of the GaN sample as well as of a Si sample implanted with overlapping profiles of Eu-151 and O. The GaN spectra were fitted with two symmetric doublets, D1 and D2, with isomer shifts and quadrupole splittings of delta = -0.27 mm/s (relative to Eu2O3), Delta E-Q = 0.85 (3) mm/s; and delta = - 0.22 mm/s, Delta E-Q = 2.90 (5) mm/s, respectively. D1 is attributed to Eu at substitutional Ga lattice sites; D2 to Eu at or near substitutional sites but with extensive lattice damage. The splittings of D1 and D2 correspond to quadrupole coupling frequency of 15 (2) and 50 (4) MHz, consistent with measurements of Ga-69, Ga-71 and In-111 in GaN."],["dc.identifier.doi","10.1007/s10751-008-9792-8"],["dc.identifier.isi","000261061400034"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/54136"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Springer"],["dc.relation.issn","0304-3843"],["dc.title","Electric field gradients at Eu-151 sites in GaN"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","PII S0925-9635(02)00236-4"],["dc.bibliographiccitation.firstpage","1182"],["dc.bibliographiccitation.issue","3-7"],["dc.bibliographiccitation.journal","Diamond and Related Materials"],["dc.bibliographiccitation.lastpage","1185"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Vetter, Ulrich"],["dc.contributor.author","Reinke, Petra"],["dc.contributor.author","Ronning, Carsten"],["dc.contributor.author","Hofsass, H."],["dc.contributor.author","Schaaf, Peter"],["dc.contributor.author","Bharuth-Ram, K."],["dc.contributor.author","Taniguchi, T."],["dc.date.accessioned","2018-11-07T10:40:18Z"],["dc.date.available","2018-11-07T10:40:18Z"],["dc.date.issued","2003"],["dc.description.abstract","We investigated the doping of thin films of tetrahedral amorphous carbon (ta-C) and cubic boron nitride (c-BN) with europium. The films were grown by mass selected ion beam deposition and doped with europium during growth. Analysis was performed in vacuo using photoelectron spectroscopy and ex vacuo with conversion electron Mossbauer, Fourier transform infrared and cathodoluminescence spectroscopy. Successful incorporation of europium into the c-BN films is achieved. These c-BN:Eu films show luminescence of the D-5(0)-F-7(2) intra-4f electron transition, measured at 12 and 300 K. The results are compared to Eu implanted poly crystalline c-BN. In case of the ta-C films doped with Eu during growth an accumulation of the deposited Eu atoms at the surface is observed. (C) 2002 Elsevier Science B.V. All rights reserved."],["dc.identifier.doi","10.1016/S0925-9635(02)00236-4"],["dc.identifier.isi","000182872000182"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/46271"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Sa"],["dc.publisher.place","Lausanne"],["dc.relation.conference","13th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides and Sililcon Carbide (Diamond 2002)"],["dc.relation.eventlocation","GRANADA, SPAIN"],["dc.relation.issn","0925-9635"],["dc.title","Europium doping of c-BN and ta-C thin films"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","PII S0257-8972(02)00248-7"],["dc.bibliographiccitation.firstpage","382"],["dc.bibliographiccitation.journal","Surface and Coatings Technology"],["dc.bibliographiccitation.lastpage","387"],["dc.bibliographiccitation.volume","158"],["dc.contributor.author","Ronning, Carsten"],["dc.contributor.author","Schwen, Daniel"],["dc.contributor.author","Eyhusen, S."],["dc.contributor.author","Vetter, Ulrich"],["dc.contributor.author","Hofsass, H."],["dc.date.accessioned","2018-11-07T10:09:02Z"],["dc.date.available","2018-11-07T10:09:02Z"],["dc.date.issued","2002"],["dc.description.abstract","We have grown boron carbide (BxC) thin films via direct ion beam deposition using mass selected B-11(+) and C-12(+) ions. The films were deposited on silicon and ITO-coated quartz glass substrates with an ion energy of 100 eV at room temperature. The B+:C+ ion ratio during deposition was varied between 0:1 (pure carbon) and 1:0 (pure boron), and the resulting composition of the films matched this ratio, as observed by X-ray photoelectron spectroscopy (XPS). A detailed analysis of the XPS-spectra revealed that the deposited films undergo a transition from sp(3)-bonded diamond-like carbon to a boron carbide phase with a lower density with increasing B concentration. The formation of carbide bonds has been observed by means of XPS, and the valence band spectra showed a strong transition from the amorphous semiconductor ta-C to metallic boron. This transition has also been observed by optical and electrical measurements. (C) 2002 Elsevier Science B.V. All rights reserved."],["dc.identifier.doi","10.1016/S0257-8972(02)00248-7"],["dc.identifier.isi","000178482100070"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/39586"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Sa"],["dc.publisher.place","Lausanne"],["dc.relation.eventlocation","MARBURG, GERMANY"],["dc.relation.issn","0257-8972"],["dc.title","Ion beam synthesis of boron carbide thin films"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","55"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Diamond and Related Materials"],["dc.bibliographiccitation.lastpage","60"],["dc.bibliographiccitation.volume","15"],["dc.contributor.author","Chan, C. Y."],["dc.contributor.author","Eyhusen, S."],["dc.contributor.author","Meng, X. M."],["dc.contributor.author","Bello, I."],["dc.contributor.author","Lee, S. T."],["dc.contributor.author","Ronning, Carsten"],["dc.contributor.author","Hofsass, H."],["dc.date.accessioned","2018-11-07T10:33:24Z"],["dc.date.available","2018-11-07T10:33:24Z"],["dc.date.issued","2006"],["dc.description.abstract","Boron nitride (BN) films have been deposited on silicon (Si) substrates with a root-mean-square surface roughness between 0.2 and 170 nm using mass-selected ion beam deposition (MSIBD). Mechanical scratching by either diamond or alumina powders with different powder sizes was used for substrate pretreatment. The effect of substrate surface roughness on the subsequent growth of BN films at different ion energies (75-500 eV) was investigated by Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and transmission electron microscopy (TEM). For rough substrates the surface morphology of the BN films changes from a granular structure at low ion energies to a flat and featureless surface at 500 eV ion energy. In the latter case grooves and valleys are first filled up with amorphous BN before turbostratic BN (t-BN) is formed. Eventually c-BN nucleates on the t-BN interfacial layer. The c-BN nucleation threshold energy of about 125 eV remains unchanged. Surface-like growth processes dominate at low ion energy, leading to the granular morphology. The observations are explained by ion impact on inclined micro-surfaces, leading to reduced projected ion ranges and enhanced sputtering and redeposition into surface grooves and valleys. (c) 2005 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.diamond.2005.07.009"],["dc.identifier.isi","000234605900010"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/44602"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Sa"],["dc.relation.issn","0925-9635"],["dc.title","The effect of substrate surface roughness on the nucleation of cubic boron nitride films"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","054126"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","PHYSICAL REVIEW B"],["dc.bibliographiccitation.volume","72"],["dc.contributor.author","Eyhusen, S."],["dc.contributor.author","Ronning, Carsten"],["dc.contributor.author","Hofsass, H."],["dc.date.accessioned","2018-11-07T11:18:11Z"],["dc.date.available","2018-11-07T11:18:11Z"],["dc.date.issued","2005"],["dc.description.abstract","Cubic boron nitride (c-BN) thin films were deposited on silicon substrates using mass separated ion beam deposition (MSIBD). In order to investigate the influence of the ion energy on the growth of c-BN films, B-11(+) and N-14(+) ions were implanted into c-BN with ion energies ranging from 5 keV to 43 keV and substrate temperatures (T-S) from room temperature (RT) to 250 degrees C. A systematic study on the interplay of E-ion and T-S has revealed a characteristic energy-dependent temperature threshold for c-BN growth. This behavior is explained by dynamic annealing of defects caused by a penetrating ion in a collison cascade. In this picture, the suppression of defect accumulation that is crucial for maintaining cubic phase formation is attributed to temperature-driven back diffusion and subsequent annihilation of B and N interstitial recoils. The model is confirmed by analyzing the depth profile of implanted, isotopically pure B-10, and its application for both c-BN nucleation and growth is discussed."],["dc.identifier.doi","10.1103/PhysRevB.72.054126"],["dc.identifier.isi","000231564300063"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/54981"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","American Physical Soc"],["dc.relation.issn","1098-0121"],["dc.title","Cubic boron nitride thin film growth by boron and nitrogen ion implantation"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","034307"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Journal of Applied Physics"],["dc.bibliographiccitation.volume","98"],["dc.contributor.author","Ronning, Carsten"],["dc.contributor.author","Shang, N. G."],["dc.contributor.author","Gerhards, Inga"],["dc.contributor.author","Hofsass, H."],["dc.contributor.author","Seibt, M."],["dc.date.accessioned","2018-11-07T10:35:14Z"],["dc.date.available","2018-11-07T10:35:14Z"],["dc.date.issued","2005"],["dc.description.abstract","Tetrapod zinc oxide (T-ZnO) nanorods have been synthesized by evaporation and recondensation of metallic Zn under ambient conditions. The total sizes of the T-ZnO nanostructures range from 300 nm to 15 mu m with leg diameters of about 30 to 650 nm, depending on the deposition temperature. A detailed high-resolution electron microscopy analysis showed that the center core of T-ZnO nanorods consists of four hexagonal grains with a twinlike relation. The nucleation and growth mechanism has been generated on the basis of energy considerations during a phase transition from a fullerenelike ZnO cluster to a nanometer-sized tetrahedron, which is directly visible in our high-resolution transmission electron microscopy investigations. (c) 2005 American Institute of Physics."],["dc.identifier.doi","10.1063/1.1997290"],["dc.identifier.isi","000231246100092"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/45045"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Inst Physics"],["dc.relation.issn","0021-8979"],["dc.title","Nucleation mechanism of the seed of tetrapod ZnO nanostructures"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]