Willke, Philip

[["dc.bibliographiccitation.firstpage","226"],["dc.bibliographiccitation.issue","7644"],["dc.bibliographiccitation.journal","Nature"],["dc.bibliographiccitation.lastpage","+"],["dc.bibliographiccitation.volume","543"],["dc.contributor.author","Natterer, Fabian D."],["dc.contributor.author","Yang, Kai"],["dc.contributor.author","Paul, William"],["dc.contributor.author","Willke, Philip"],["dc.contributor.author","Choi, Taeyoung"],["dc.contributor.author","Greber, Thomas"],["dc.contributor.author","Heinrich, Andreas J."],["dc.contributor.author","Lutz, Christopher P."],["dc.date.accessioned","2018-11-07T10:26:16Z"],["dc.date.available","2018-11-07T10:26:16Z"],["dc.date.issued","2017"],["dc.description.abstract","The single-atom bit represents the ultimate limit of the classical approach to high-density magnetic storage media. So far, the smallest individually addressable bistable magnetic bits have consisted of 3-12 atoms(1-3). Long magnetic relaxation times have been demonstrated for single lanthanide atoms in molecular magnets(4-12), for lanthanides diluted in bulk crystals(13), and recently for ensembles of holmium (Ho) atoms supported on magnesium oxide (MgO)(14). These experiments suggest a path towards data storage at the atomic limit, but the way in which individual magnetic centres are accessed remains unclear. Here we demonstrate the reading and writing of the magnetism of individual Ho atoms on MgO, and show that they independently retain their magnetic information over many hours. We read the Ho states using tunnel magnetoresistance(15,16) and write the states with current pulses using a scanning tunnelling microscope. The magnetic origin of the long-lived states is confirmed by single-atom electron spin resonance(17) on a nearby iron sensor atom, which also shows that Ho has a large out-of-plane moment of 10.1 +/- 0.1 Bohr magnetons on this surface. To demonstrate independent reading and writing, we built an atomic-scale structure with two Ho bits, to which we write the four possible states and which we read out both magnetoresistively and remotely by electron spin resonance. The high magnetic stability combined with electrical reading and writing shows that single-atom magnetic memory is indeed possible."],["dc.identifier.doi","10.1038/nature21371"],["dc.identifier.isi","000395688700035"],["dc.identifier.pmid","28277519"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/43004"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.publisher","Nature Publishing Group"],["dc.relation.issn","1476-4687"],["dc.relation.issn","0028-0836"],["dc.title","Reading and writing single-atom magnets"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","eaaq1543"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Science Advances"],["dc.bibliographiccitation.volume","4"],["dc.contributor.author","Willke, Philip"],["dc.contributor.author","Paul, William"],["dc.contributor.author","Natterer, Fabian D."],["dc.contributor.author","Yang, Kai"],["dc.contributor.author","Bae, Yujeong"],["dc.contributor.author","Choi, Taeyoung"],["dc.contributor.author","Fernández-Rossier, Joaquin"],["dc.contributor.author","Heinrich, Andreas J."],["dc.contributor.author","Lutz, Christoper P."],["dc.date.accessioned","2020-12-10T18:36:38Z"],["dc.date.available","2020-12-10T18:36:38Z"],["dc.date.issued","2018"],["dc.identifier.doi","10.1126/sciadv.aaq1543"],["dc.identifier.eissn","2375-2548"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/76697"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Probing quantum coherence in single-atom electron spin resonance"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","6039"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","ACS Applied Materials & Interfaces"],["dc.bibliographiccitation.lastpage","6045"],["dc.bibliographiccitation.volume","10"],["dc.contributor.author","Momeni Pakdehi, D."],["dc.contributor.author","Aprojanz, J."],["dc.contributor.author","Sinterhauf, A."],["dc.contributor.author","Pierz, K."],["dc.contributor.author","Kruskopf, M."],["dc.contributor.author","Willke, P."],["dc.contributor.author","Baringhaus, J."],["dc.contributor.author","Stöckmann, J. P."],["dc.contributor.author","Traeger, G. A."],["dc.contributor.author","Hohls, F."],["dc.contributor.author","Tegenkamp, C."],["dc.contributor.author","Wenderoth, M."],["dc.contributor.author","Ahlers, F. J."],["dc.contributor.author","Schumacher, H. W."],["dc.date.accessioned","2020-12-10T15:22:29Z"],["dc.date.available","2020-12-10T15:22:29Z"],["dc.date.issued","2018"],["dc.identifier.doi","10.1021/acsami.7b18641"],["dc.identifier.eissn","1944-8252"],["dc.identifier.issn","1944-8244"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/73416"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Minimum Resistance Anisotropy of Epitaxial Graphene on SiC"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1700003"],["dc.bibliographiccitation.issue","11"],["dc.bibliographiccitation.journal","Annalen der Physik"],["dc.bibliographiccitation.volume","529"],["dc.contributor.author","Willke, P."],["dc.contributor.author","Schneider, M. A."],["dc.contributor.author","Wenderoth, M."],["dc.date.accessioned","2020-12-10T14:07:54Z"],["dc.date.available","2020-12-10T14:07:54Z"],["dc.date.issued","2017"],["dc.identifier.doi","10.1002/andp.201700003"],["dc.identifier.issn","0003-3804"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/70327"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Electronic Transport Properties of 1D-Defects in Graphene and Other 2D-Systems"],["dc.title.alternative","Electronic transport properties of 1D-defects in graphene and other 2D-systems"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","5110"],["dc.bibliographiccitation.issue","8"],["dc.bibliographiccitation.journal","Nano Letters"],["dc.bibliographiccitation.lastpage","5115"],["dc.bibliographiccitation.volume","15"],["dc.contributor.author","Willke, Philip"],["dc.contributor.author","Amani, Julian Alexander"],["dc.contributor.author","Sinterhauf, Anna"],["dc.contributor.author","Thakur, Sangeeta"],["dc.contributor.author","Kotzott, Thomas"],["dc.contributor.author","Druga, Thomas"],["dc.contributor.author","Weikert, Steffen"],["dc.contributor.author","Maiti, Kalobaran"],["dc.contributor.author","Hofsaess, Hans"],["dc.contributor.author","Wenderoth, Martin"],["dc.date.accessioned","2018-11-07T09:53:46Z"],["dc.date.available","2018-11-07T09:53:46Z"],["dc.date.issued","2015"],["dc.description.abstract","We investigate the structural, electronic, and transport properties of substitutional defects in SiC-graphene by means of scanning tunneling microscopy and magnetotransport experiments. Using ion incorporation via ultralow energy ion implantation, the influence of different ion species (boron, nitrogen, and carbon) can directly be compared. While boron and nitrogen atoms lead to an effective doping of the graphene sheet and can reduce or raise the position of the Fermi level, respectively, C-12(+) carbon ions are used to study possible defect creation by the bombardment. For low-temperature transport, the implantation leads to an increase in resistance and a decrease in mobility in contrast to undoped samples. For undoped samples, we observe in high magnetic fields a positive magnetoresistance that changes to negative for the doped samples, especially for B-11(+)- and C-12(+)-ions. We conclude that the conductivity of the graphene sheet is lowered by impurity atoms and especially by lattice defects, because they result in weak localization effects at low temperatures."],["dc.identifier.doi","10.1021/acs.nanolett.5b01280"],["dc.identifier.isi","000359613700039"],["dc.identifier.pmid","26120803"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/36396"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1530-6992"],["dc.relation.issn","1530-6984"],["dc.title","Doping of Graphene by Low-Energy Ion Beam Implantation: Structural, Electronic, and Transport Properties"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","470"],["dc.bibliographiccitation.journal","Carbon"],["dc.bibliographiccitation.lastpage","476"],["dc.bibliographiccitation.volume","102"],["dc.contributor.author","Willke, Philip"],["dc.contributor.author","Moehle, Christian"],["dc.contributor.author","Sinterhauf, Anna"],["dc.contributor.author","Kotzott, Thomas"],["dc.contributor.author","Yu, H. K."],["dc.contributor.author","Wodtke, Alec"],["dc.contributor.author","Wenderoth, Martin"],["dc.date.accessioned","2018-11-07T10:14:01Z"],["dc.date.available","2018-11-07T10:14:01Z"],["dc.date.issued","2016"],["dc.description.abstract","By using Kelvin Probe Force Microscopy with an additional applied electric field we investigate the local voltage drop in graphene on SiO2 under ambient conditions. We are able to quantify the variation of the local sheet resistance and to resolve localized voltage drops at line defects. Our data demonstrates that the resistance of line defects has been overestimated so far. Moreover, we show that wrinkles have the largest resistance, rho(Wrinkle) < 80 Omega mu m. Temperature-dependent measurements show that the local monolayer sheet resistance reflects the macroscopic increase in resistance with temperature while the defect resistance for folded wrinkles is best described by a temperature-independent model which we attribute to interlayer tunneling. (C) 2016 Elsevier Ltd. All rights reserved."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft (DFG)"],["dc.identifier.doi","10.1016/j.carbon.2016.02.067"],["dc.identifier.isi","000372808200052"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/40547"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Pergamon-elsevier Science Ltd"],["dc.relation.issn","1873-3891"],["dc.relation.issn","0008-6223"],["dc.title","Local transport measurements in graphene on SiO2 using Kelvin probe force microscopy"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","166401"],["dc.bibliographiccitation.issue","16"],["dc.bibliographiccitation.journal","Physical Review Letters"],["dc.bibliographiccitation.volume","128"],["dc.contributor.author","Pramanik, Arindam"],["dc.contributor.author","Thakur, Sangeeta"],["dc.contributor.author","Singh, Bahadur"],["dc.contributor.author","Willke, Philip"],["dc.contributor.author","Wenderoth, Martin"],["dc.contributor.author","Hofsäss, Hans"],["dc.contributor.author","Di Santo, Giovanni"],["dc.contributor.author","Petaccia, Luca"],["dc.contributor.author","Maiti, Kalobaran"],["dc.date.accessioned","2022-06-01T09:39:25Z"],["dc.date.available","2022-06-01T09:39:25Z"],["dc.date.issued","2022"],["dc.description.sponsorship"," Department of Atomic Energy, Government of India"],["dc.description.sponsorship"," Elettra-Sincrotrone Trieste"],["dc.description.sponsorship"," Board of Research in Nuclear Sciences"],["dc.identifier.doi","10.1103/PhysRevLett.128.166401"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/108470"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-572"],["dc.relation.eissn","1079-7114"],["dc.relation.issn","0031-9007"],["dc.rights.uri","https://link.aps.org/licenses/aps-default-license"],["dc.title","Anomalies at the Dirac Point in Graphene and Its Hole-Doped Compositions"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","125412"],["dc.bibliographiccitation.issue","12"],["dc.bibliographiccitation.journal","PHYSICAL REVIEW B"],["dc.bibliographiccitation.volume","89"],["dc.contributor.author","Kloth, Philipp"],["dc.contributor.author","Wenderoth, Martin"],["dc.contributor.author","Willke, Philip"],["dc.contributor.author","Prueser, Henning"],["dc.contributor.author","Ulbrich, Rainer G."],["dc.date.accessioned","2018-11-07T09:42:38Z"],["dc.date.available","2018-11-07T09:42:38Z"],["dc.date.issued","2014"],["dc.description.abstract","Using low-temperature scanning tunneling spectroscopy we study quantum well states in the topmost copper layer of a Cu/Co/Cu(100) system above the Fermi energy. The emergence and the energetic positions of QWSs within this layer crucially depend on the interface quality tailored by the sample preparation method. Samples deposited at room temperature show a rough interface and lead to the well-known QWSs with only a momentum perpendicular to the interface. Atomically smooth interfaces for samples grown at 80 K exhibit states caused by stationary points with a large nonvanishing parallel momentum. Simulations taking into account the different band structures allow QWSs to be modeled from both stationary points and an identification of a crossover between bound and resonance states."],["dc.identifier.doi","10.1103/PhysRevB.89.125412"],["dc.identifier.isi","000332505500013"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/34001"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Physical Soc"],["dc.relation.issn","2469-9969"],["dc.relation.issn","2469-9950"],["dc.title","Quantum well states with nonvanishing parallel momentum in Cu/Co/Cu(100)"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","111605"],["dc.bibliographiccitation.issue","11"],["dc.bibliographiccitation.journal","Applied Physics Letters"],["dc.bibliographiccitation.volume","105"],["dc.contributor.author","Willke, Philip"],["dc.contributor.author","Amani, Julian Alexander"],["dc.contributor.author","Thakur, S."],["dc.contributor.author","Weikert, Steffen"],["dc.contributor.author","Druga, T."],["dc.contributor.author","Maiti, Kalobaran"],["dc.contributor.author","Hofsaess, H."],["dc.contributor.author","Wenderoth, Martin"],["dc.date.accessioned","2018-11-07T09:35:13Z"],["dc.date.available","2018-11-07T09:35:13Z"],["dc.date.issued","2014"],["dc.description.abstract","We perform a structural analysis of nitrogen-doped graphene on SiC(0001) prepared by ultra low-energy ion bombardment. Using scanning tunneling microscopy, we show that nitrogen atoms are incorporated almost exclusively as graphitic substitution in the graphene honeycomb lattice. With an irradiation energy of 25 eV arid a tluence of approximately 5 x 10(14) cm(-2), we achieve a nitrogen content of around 1%. By quantitatively comparing the position of the N-atoms in the topography measurements with simulated random distributions, we find statistically significant short-range correlations. Consequently, we are able to show that the dopants arrange preferably at lattice sites given by the 6 x 6-reconstruction of the underlying substrate. This selective incorporation is most likely triggered by adsorbate layers present during the ion bombardment. This study identifies low-energy ion irradiation as a promising method for controlled doping in epitaxial graphene. (C) 2014 AIP Publishing LLC."],["dc.identifier.doi","10.1063/1.4895801"],["dc.identifier.isi","000342995800024"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/32338"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1077-3118"],["dc.relation.issn","0003-6951"],["dc.title","Short-range ordering of ion-implanted nitrogen atoms in SiC-graphene"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","6399"],["dc.bibliographiccitation.journal","Nature Communications"],["dc.bibliographiccitation.volume","6"],["dc.contributor.author","Willke, Philip"],["dc.contributor.author","Druga, Thomas"],["dc.contributor.author","Ulbrich, Rainer G."],["dc.contributor.author","Schneider, M. Alexander"],["dc.contributor.author","Wenderoth, Martin"],["dc.date.accessioned","2018-11-07T10:00:09Z"],["dc.date.available","2018-11-07T10:00:09Z"],["dc.date.issued","2015"],["dc.description.abstract","Electronic transport on a macroscopic scale is described by spatially averaged electric fields and scattering processes summarized in a reduced electron mobility. That this does not capture electronic transport on the atomic scale was realized by Landauer long ago. Local and non-local scattering processes need to be considered separately, the former leading to a voltage drop localized at a defect, the so-called Landauer residual-resistivity dipole. Lacking precise experimental data on the atomic scale, the spatial extent of the voltage drop remained an open question. Here, we provide an experimental study showing that the voltage drop at a monolayer-bilayer boundary in graphene clearly extends spatially up to a few nanometres into the bilayer and hence is not located strictly at the structural defect. Moreover, different scattering mechanisms can be disentangled. The matching of wave functions at either side of the junction is identified as the dominant process, a situation similar to that encountered when a molecule bridges two contacts."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft (DFG) priority program 1459 Graphene"],["dc.identifier.doi","10.1038/ncomms7399"],["dc.identifier.isi","000352633400012"],["dc.identifier.pmid","25744816"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/37739"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Nature Publishing Group"],["dc.relation.issn","2041-1723"],["dc.title","Spatial extent of a Landauer residual-resistivity dipole in graphene quantified by scanning tunnelling potentiometry"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]