Hofsäss, Hans Christian

[["dc.bibliographiccitation.firstpage","1176"],["dc.bibliographiccitation.issue","9"],["dc.bibliographiccitation.journal","Optical Materials Express"],["dc.bibliographiccitation.lastpage","1185"],["dc.bibliographiccitation.volume","2"],["dc.contributor.author","Gruber, John B."],["dc.contributor.author","Burdick, Gary W."],["dc.contributor.author","Vetter, Ulrich"],["dc.contributor.author","Mitchell, Brandon"],["dc.contributor.author","Dierolf, Volkmar"],["dc.contributor.author","Hofsäss, Hans"],["dc.date.accessioned","2012-08-09T12:54:24Z"],["dc.date.accessioned","2021-10-11T11:26:10Z"],["dc.date.available","2012-08-09T12:54:24Z"],["dc.date.available","2021-10-11T11:26:10Z"],["dc.date.issued","2012"],["dc.description.abstract","The crystal-field and Zeeman splittings of the energy levels of Nd3+(4f3) 2S+1LJ in hexagonal phase AlN have been investigated. The multiplet manifolds of Nd3+(4f3) analyzed include the ground state, 4I9/2, and excited states 4I11/2, 4I13/2, 4F3/2, 4F5/2, 2H(2)9/2, 4F7/2, 4S3/2, 4G5/2, and 2G7/2. Experimental energy levels were obtained from analyses of the 12 K cathodoluminescence spectra from Nd3+-implanted films of AlN, and from the 15 K photoluminescence excitation spectra and the site-selective combined excitation-emission spectra (CEES) recently reported for in situ Nd-doped hexagonal AlN grown by plasma-assisted molecular beam epitaxy (PA-MBE). CEES results identify a main site and two minority sites for Nd3+ in both samples. Transition line strengths attributed to the ion in minority sites are relatively stronger in Nd:AlN than in Nd:GaN. The 15 K experimental Zeeman splitting of Nd3+ are analyzed in the PA-MBE grown AlN samples and compared with the Zeeman splitting observed in Nd:GaN. The crystal-field and Zeeman splittings were modeled using a parametrized Hamiltonian consisting of atomic and crystal-field terms. We considered possible site distortion due to the size of the implanted Nd ion that would reduce the site symmetry from C3v to C3 or C1h. However, no significant improvement was obtained using these lower symmetry models, leading us to conclude that C3v symmetry is a reasonable approximation for the main site Nd3+ ions in AlN."],["dc.description.sponsorship","Open-Access-Publikationsfonds 2012"],["dc.identifier.doi","10.1364/OME.2.001176"],["dc.identifier.isi","000308598300001"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/7850"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/90544"],["dc.language.iso","en"],["dc.notes.intern","Migrated from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Optical Soc Amer"],["dc.relation.issn","2159-3930"],["dc.relation.orgunit","Fakultät für Physik"],["dc.rights","Goescholar"],["dc.rights.access","openAccess"],["dc.rights.uri","https://goedoc.uni-goettingen.de/licenses"],["dc.subject","Atomic and molecular physics : Zeeman effect; Physical optics : Luminescence; Physical optics : Stark effect"],["dc.title","Crystal field and Zeeman splittings for energy levels of Nd3+ in hexagonal AlN"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","025011"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Journal of Micromechanics and Microengineering"],["dc.bibliographiccitation.volume","22"],["dc.contributor.author","Schulte-Borchers, Martina"],["dc.contributor.author","Vetter, Ulrich"],["dc.contributor.author","Koppe, Tristan"],["dc.contributor.author","Hofsaess, H."],["dc.date.accessioned","2018-11-07T09:13:54Z"],["dc.date.available","2018-11-07T09:13:54Z"],["dc.date.issued","2012"],["dc.description.abstract","We report on a new method of three-dimensional structuring by means of proton beam writing in p-type gallium arsenide. While up to now vertical features have been created by varying the proton beam energy during irradiation which changes the proton penetration depth and thereby the depth of the material modification, we manufactured 3D structures with a single beam energy but different proton doses supplemented by a subsequent controlled electrochemical etching process. This new approach could simplify 3D structuring in semiconductors and the usage of proton beam writing for the manufacturing of micro electromechanical devices with high aspect ratios and smooth sidewalls."],["dc.description.sponsorship","University of Melbourne"],["dc.identifier.doi","10.1088/0960-1317/22/2/025011"],["dc.identifier.isi","000299959000011"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/27276"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Iop Publishing Ltd"],["dc.relation.issn","0960-1317"],["dc.title","3D microstructuring in p-GaAs with proton beam writing using multiple ion fluences"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","782"],["dc.bibliographiccitation.issue","5-6"],["dc.bibliographiccitation.journal","Diamond and Related Materials"],["dc.bibliographiccitation.lastpage","784"],["dc.bibliographiccitation.volume","20"],["dc.contributor.author","Vetter, Ulrich"],["dc.contributor.author","Mueller, Sven"],["dc.contributor.author","Broetzmann, Marc"],["dc.contributor.author","Hofsaess, Hans"],["dc.contributor.author","Gruber, John B."],["dc.date.accessioned","2018-11-07T08:56:18Z"],["dc.date.available","2018-11-07T08:56:18Z"],["dc.date.issued","2011"],["dc.description.abstract","We report on the effective reduction of AlN host lattice defect cathodoluminescence by high dose ion implantation of light elements such as fluorine as well as chlorine and neon with peak concentrations of 1 at.%. In order to distinguish between luminescence suppression in the visible to luminescence quenching due to radiation damage, all samples were additionally implanted with europium at fluences of 1.10(13) ions/cm(2). After annealing the samples at 1373 K under vacuum conditions cathodoluminescence spectra were recorded at room temperature (300 K) and at cryogenic temperature (12 K). These investigations reveal that different light ion species have different influences on the defect luminescence of the AlN host lattice which is likely due to selective passivation of these defects. The best ratio of defect luminescence suppression to radiation damage induced luminescence quenching is achieved in the case of fluorine co-doping. (C) 2011 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.diamond.2011.03.038"],["dc.identifier.isi","000291775700027"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/23111"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Sa"],["dc.relation.issn","0925-9635"],["dc.title","Effective reduction of AlN defect luminescence by fluorine implantation"],["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","295501"],["dc.bibliographiccitation.issue","29"],["dc.bibliographiccitation.journal","Journal of Physics Condensed Matter"],["dc.bibliographiccitation.volume","26"],["dc.contributor.author","Bruesewitz, Christoph"],["dc.contributor.author","Vetter, Ulrich"],["dc.contributor.author","Hofsaess, H."],["dc.contributor.author","Barsoum, Michel W."],["dc.date.accessioned","2018-11-07T09:37:33Z"],["dc.date.available","2018-11-07T09:37:33Z"],["dc.date.issued","2014"],["dc.description.abstract","We use the perturbed angular correlation method with In-111-Cd-111 probe atoms to in situ study the changes in the electric field gradient at room temperature of polycrystalline Ti2AlN and Nb2AlC, titanium and zinc, and rutile samples, as a function of cyclic uniaxial compressive loads. The load dependence of the quadrupole coupling constant v(Q) was found to be large in titanium and zinc but small in Ti2AlN, Nb2AlC and rutile. Reversible and irreversible increases in the electric field gradient distribution widths were found under load and after releasing the load, respectively. Annihilation of dislocations, as well as elastic deformation, are considered to contribute to the reversible behavior. The irreversible response must be caused by a permanent increase in dislocation and point defect densities. The deformation induced broadening of the electric field gradient can be recovered by post-annealing of the deformed sample."],["dc.identifier.doi","10.1088/0953-8984/26/29/295501"],["dc.identifier.isi","000339710100007"],["dc.identifier.pmid","24957211"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/32865"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Iop Publishing Ltd"],["dc.relation.issn","1361-648X"],["dc.relation.issn","0953-8984"],["dc.title","Perturbed angular correlation studies of uniaxial compressive stressed zinc, titanium, rutile, Ti2AlN, and Nb2AlC"],["dc.type","journal_article"],["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.issue","1"],["dc.bibliographiccitation.journal","Scientific Reports"],["dc.bibliographiccitation.volume","10"],["dc.contributor.author","Mahata, Manoj Kumar"],["dc.contributor.author","Koppe, Tristan"],["dc.contributor.author","Kumar, Kaushal"],["dc.contributor.author","Hofsäss, Hans"],["dc.contributor.author","Vetter, Ulrich"],["dc.date.accessioned","2021-04-14T08:25:46Z"],["dc.date.available","2021-04-14T08:25:46Z"],["dc.date.issued","2020"],["dc.description.sponsorship","Open-Access-Publikationsfonds 2020"],["dc.identifier.doi","10.1038/s41598-020-65149-z"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/17462"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/81727"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-399"],["dc.notes.intern","Merged from goescholar"],["dc.relation.eissn","2045-2322"],["dc.relation.orgunit","Fakultät für Physik"],["dc.rights","CC BY 4.0"],["dc.rights.uri","http://creativecommons.org/licenses/by/4.0/"],["dc.title","Upconversion photoluminescence of Ho3+-Yb3+ doped barium titanate nanocrystallites: Optical tools for structural phase detection and temperature probing"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","607"],["dc.bibliographiccitation.journal","HYPERFINE INTERACTIONS"],["dc.bibliographiccitation.lastpage","612"],["dc.bibliographiccitation.volume","136"],["dc.contributor.author","Vetter, Ulrich"],["dc.contributor.author","Uhrmacher, Michael"],["dc.contributor.author","Schwen, Daniel"],["dc.contributor.author","Lohstroh, A."],["dc.contributor.author","Hofsass, H."],["dc.contributor.author","Lieb, Klaus-Peter"],["dc.date.accessioned","2018-11-07T09:33:47Z"],["dc.date.available","2018-11-07T09:33:47Z"],["dc.date.issued","2001"],["dc.description.abstract","The lattice sites of implanted In atoms in Cr2O3 were investigated by means of electron emission channeling (EC) measurements using In-111 probe atoms. EC spectra were recorded for several axes and compared to simulations. Indium atoms are most likely located at near-Cr sites. Small differences in the EC patterns for prompt and delayed electrons may be an indication for displacements of Cd-111 emitter atoms following the electron capture decay of In."],["dc.identifier.doi","10.1023/A:1020574406411"],["dc.identifier.isi","000178528100074"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/32041"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Kluwer Academic Publ"],["dc.publisher.place","Dordrecht"],["dc.relation.conference","12th International Conference on Hyperfine Interactions"],["dc.relation.eventlocation","PARK CITY, UTAH"],["dc.relation.issn","0304-3843"],["dc.title","Lattice location studies of indium in Cr2O3"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","205201"],["dc.bibliographiccitation.issue","20"],["dc.bibliographiccitation.journal","PHYSICAL REVIEW B"],["dc.bibliographiccitation.volume","74"],["dc.contributor.author","Vetter, Ulrich"],["dc.contributor.author","Gruber, John B."],["dc.contributor.author","Nijjar, Anmol S."],["dc.contributor.author","Zandi, Bahram"],["dc.contributor.author","Oehl, Gregor"],["dc.contributor.author","Wahl, Ulrich"],["dc.contributor.author","De Vries, Bart"],["dc.contributor.author","Hofsaess, Hans"],["dc.contributor.author","Dietrich, Marc"],["dc.date.accessioned","2018-11-07T09:04:03Z"],["dc.date.available","2018-11-07T09:04:03Z"],["dc.date.issued","2006"],["dc.description.abstract","We report a detailed crystal field analysis of Pm3+ and Sm3+ as well as lattice location studies of Pm-147 and Nd-147 in 2H-aluminum nitride (w-AlN). The isotopes of mass 147 were produced by nuclear fission and implanted at an energy of 60 keV. The decay chain of interest in this work is Nd-147 -> Pm-147 -> Sm-147 (stable). Lattice location studies applying the emission channeling technique were carried out using the beta(-) particles and conversion electrons emitted in the radioactive decay of Nd-147 -> Pm-147. The samples were investigated as implanted, and also they were investigated after annealing to temperatures of 873 K as well as 1373 K. The main fraction of about 60% of both Pm-147 as well as Nd-147 atoms was located on substitutional Al sites in the AlN lattice; the remainder of the ions were located randomly within the AlN lattice. Following radioactive decay of Nd-147, the cathodoluminescence spectra of Pm3+ and Sm3+ were obtained between 500 nm and 1050 nm at sample temperatures between 12 K and 300 K. High-resolution emission spectra, representing intra-4f electron transitions, were analyzed to establish the crystal-field splitting of the energy levels of Sm3+ (4f(5)) and Pm3+ (4f(4)) in cationic sites having C-3v symmetry in the AlN lattice. Using crystal-field splitting models, we obtained a rms deviation of 6 cm(-1) between 31 calculated-to-experimental energy (Stark) levels for Sm3+ in AlN. The results are similar to those reported for Sm3+ implanted into GaN. Using a set of crystal-field splitting parameters B-nm, for Pm3+ derived from the present Sm3+ analysis, we calculated the splitting for the F-5(1), I-5(4), and I-5(5) multiplet manifolds in Pm3+ and obtained good agreement between the calculated and the experimental Stark levels. Temperature-dependent lifetime measurements are also reported for the emitting levels F-4(5/2) (Sm3+) and F-5(1) (Pm3+)."],["dc.identifier.doi","10.1103/PhysRevB.74.205201"],["dc.identifier.isi","000242409400036"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/25023"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Physical Soc"],["dc.relation.issn","1550-235X"],["dc.relation.issn","1098-0121"],["dc.title","Crystal field analysis of Pm3+ (4f(4)) and Sm3+ (4f(5)) and lattice location studies of Nd-147 and Pm-147 in w-AlN"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","055401"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Journal of Physics Condensed Matter"],["dc.bibliographiccitation.volume","27"],["dc.contributor.author","Bruesewitz, Christoph"],["dc.contributor.author","Vetter, Ulrich"],["dc.contributor.author","Hofsaess, H."],["dc.date.accessioned","2018-11-07T10:00:59Z"],["dc.date.available","2018-11-07T10:00:59Z"],["dc.date.issued","2015"],["dc.description.abstract","We present ab-initio calculations of the independent components of gradient elastic tensors, so-called gradient elastic constants, which relate electric field gradient tensors to stress or strain tensors. The constants of cubic and hexagonal metals, MAX phases, and zinc oxide were determined within the framework of density functional theory by using the augmented plane waves plus local orbitals method implemented in the WIEN2k code. Comparison with experimental gradient elastic constants and electric field gradients' stress dependencies suggest an accuracy of about 30% of the calculated constants, independent of the probe that detects the field gradient being self- or foreign-atom. Changes in the electric field gradient take place by strain-induced asymmetric occupations of the p and d states in the valence region for all investigated materials. Volume and structural dependencies of the electric field gradient can directly be determined from this fundamental approach and are, for hexagonal closed packed metals, consistent with vanishing electric field gradients around ideal close packing and volume dependencies larger than one. The concept of these calculations is applicable in any hyperfine interaction method and, thus, can be used to gain information about intrinsic strains in systems where the experimental gradient elastic constants are inaccessible."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft (DFG) [HO 1125/19-2]"],["dc.identifier.doi","10.1088/0953-8984/27/5/055401"],["dc.identifier.isi","000348494300016"],["dc.identifier.pmid","25614685"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/37921"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Iop Publishing Ltd"],["dc.relation.issn","1361-648X"],["dc.relation.issn","0953-8984"],["dc.title","Determination of gradient elastic tensors: stress and strain dependencies of electric field gradients in cubic and hexagonal systems"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]