TY - GEN A1 - Popovici, Mihaela A1 - Delabie, Annelies A1 - Adelmann, Christoph A1 - Meersschaut, Johan A1 - Franquet, Alexis A1 - Tallarida, Massimo A1 - Berg, Jaap van den A1 - Richard, Olivier A1 - Swerts, Johan A1 - Tomida, Kazuyuki A1 - Kim, Min-Soo A1 - Tielens, Hilde A1 - Bender, Hugo A1 - Conard, Thierry A1 - Jurczak, Malgorzata A1 - Elshocht, Sven van A1 - Schmeißer, Dieter T1 - Understanding the Interface Reactions of Rutile TiO2 Grown by Atomic Layer Deposition on Oxidized Ruthenium T2 - ECS Journal of Solid State Science and Technology N2 - The atomic layer deposition of titanium oxide TiO2 on ruthenium and oxidized ruthenium with titanium methoxide as metal precursor and H2O and O3 as oxidant was investigated by Rutherford backscattering (RBS) and time of flight secondary ion mass spectrometry (TOFSIMS). An ultra-thin layer of TiO2 deposited a priori with H2O plays the role of protection of Ru(Ox) substrates against etching by O3. Information about thin films (∼3 nm) interfacial reactions, thickness and structure was brought by Medium Energy Ion Scattering Spectroscopy (MEIS) and X-ray absorption spectroscopy (XAS) measurements. The growth enhancements observed in the first stages of the deposition depends on the pre-treatment (pre-oxidation, H2O based interlayer thickness) of the Ru substrate. Thick films (∼14 nm) were analyzed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The as deposited TiO2 films are crystalline with rutile structure, as resulted from structural analyzes. However, the presence of small amounts of anatase was detected by soft X-ray absorption spectroscopy (XAS) and is strongly influenced by the surface pre-treatment of the Ru substrate. The electrical properties (equivalent oxide thickness and leakage current density) correlate with a different rutile/anatase ratio present in the films. KW - TiO2 KW - atomic layer deposition KW - rutile KW - RuOx KW - Rutherford backscattering (RBS) KW - time of flight secondary ion mass spectrometry (TOFSIMS) KW - Medium Energy Ion Scattering Spectroscopy (MEIS) KW - X-Ray absorption spectroscopy KW - transmission electron microscopy (TEM) KW - X-ray diffraction (XRD) Y1 - 2013 U6 - https://doi.org/10.1149/2.035301jss SN - 2162-8769 VL - 2 IS - 1 SP - N23 EP - N27 ER - TY - GEN A1 - Tallarida, Massimo A1 - Adelmann, Christoph A1 - Delabie, Annelies A1 - Elshocht, Sven van A1 - Caymax, Matty A1 - Schmeißer, Dieter T1 - Surface chemistry and Fermi level movement during the self-cleaning of GaAs by trimethyl-aluminum T2 - Applied physics letters Y1 - 2011 U6 - https://doi.org/10.1063/1.3615784 SN - 1077-3118 VL - 99 IS - 4 SP - 042906-1 EP - 042906-3 ER - TY - GEN A1 - Tallarida, Massimo A1 - Adelmann, Christoph A1 - Delabie, Annelies A1 - van Elshocht, Sven A1 - Caymax, Matty A1 - Schmeißer, Dieter T1 - GaAs clean up studied with synchrotron radiation photoemission T2 - IOP Conference Series : Materials Science and Engineering N2 - In this contribution we describe the chemical changes at the surface of GaAs upon adsorption of tri-methyl-aluminum (TMA). TMA is used to grow Al2O3 with atomic layer deposition (ALD) usually using H2O as oxygen source. Recently, it was pointed out that the adsorption of TMA on various III-V surfaces reduces the native oxide, allowing the growth of an abrupt III-V/High-K interface with reduced density of defects. Synchrotron radiation photoemission spectroscopy (SR-PES) is a powerful method to characterize surfaces and interfaces of many materials, as it is capable todetermine their chemical composition as well as the electronic properties. We performed in-situ SR-PES measurements after exposing a GaAs surface to TMA pulses at about 250°C. Upon using the possibility of tuning the incident photon energy we compared the Ga3d spectra at 41 eV, 71 eV, 91 eV and 121 eV, as well as the As3d at 71 eV and 91 eV. Finally, we show that using SR-PES allows a further understanding of the surface composition, which is usually not accessible with other techniques. KW - photoemission spectroscopy KW - atomic layer deposition KW - GaAs Y1 - 2012 U6 - https://doi.org/10.1088/1757-899X/41/1/012003 SN - 1757-899X IS - 41 SP - 012003 ER - TY - GEN A1 - Tallarida, Massimo A1 - Adelmann, Christoph A1 - Delabie, Annelies A1 - Elshocht, Sven van A1 - Caymax, Matty A1 - Schmeißer, Dieter T1 - III-V/Oxide Interfaces Investigated with Synchrotron Radiation Photoemission Spectroscopy T2 - ECS Transactions N2 - We used synchrotron radiation photoemission spectroscopy (SR-PES) to investigate the surface of GaAs and other III-V semiconductors after tri-methyl-aluminum (TMA) pulses performed at 250{degree sign}C. We observed the removal of native oxide and the growth of Al-oxide upon measuring the As3d, Ga3d, Al2p and VB spectra. After seven TMA pulses we performed one water pulse. As3d and Ga3d peaks showed almost no lineshape change, but a decrease of intensity due to the water adsorption. The valence band shows a change in the secondary electron cut-off and the decrease of work function. We conclude that water mostly adsorbs molecularly and induces the work function decrease. The molecular absorption of water indicates that the seven TMA pulses produce a passivated surface only partially terminated with OH groups. KW - Interfaces KW - III/V KW - Synchrotron Photoemission Spectroscopy Y1 - 2013 U6 - https://doi.org/10.1149/05004.0123ecst SN - 1938-6737 VL - 50 IS - 4 SP - 123 EP - 128 ER - TY - GEN A1 - Adelmann, Christoph A1 - Cuypers, Daniel A1 - Tallarida, Massimo A1 - Rodriguez, Leonard A1 - De Clercq, Astrid A1 - Friedrich, Daniel A1 - Conard, Thierry A1 - Delabie, Annelies A1 - Seo, Jin Won A1 - Locquet, Jean-Pierre A1 - De Gendt, Stefan A1 - Schmeißer, Dieter A1 - Elshocht, Sven van A1 - Caymax, Matty T1 - Surface Chemistry and Interface Formation during the Atomic Layer Deposition of Alumina from Trimethylaluminum and Water on Indium Phosphide T2 - Chemistry of Materials N2 - The surface chemistry and the interface formation during the initial stages of the atomic layer deposition (ALD) of Al2O3 from trimethylaluminum (TMA) and H2O on InP(100)were studied by synchrotron radiation photoemission spectroscopy and scanning tunneling microscopy. The effect of the ex situ surface cleaning by either H2SO4 or (NH4)2S was examined. It is shown that the native oxide on the InP surface consisted mainly of indium hydrogen phosphates with a P enrichment at the interface with InP. After a (NH4)2S treatment, S was present on the surface as a sulfide in both surface and subsurface sites. Exposure to TMA led to the formation of a thin AlPO4 layer, irrespective of the surface cleaning. The surface Fermi level of p-type InP was found to be pinned close to midgap after H2SO4 cleaning and moved only slightly further toward the conduction band edge upon TMA exposure, indicating that the AlPO4/InP interface was rather defective. (NH4)2S passivation led to a Fermi level position of p-type InP close to the conduction band edge. Hence, the InP surface was weakly inverted, which can be attributed to surface doping by S donors. TMA exposure was found to remove surface S, which was accompanied by a shift of the Fermi level to midgap, consistent with the removal of (part of) the S donors in combination with a defective AlPO4/InP interface. Further TMA/H2O ALD did not lead to any detectable changes of the AlPO4/InP interface and suggested simple overgrowth with Al2O3. Y1 - 2013 U6 - https://doi.org/10.1021/cm304070h SN - 1520-5002 VL - 25 IS - 7 SP - 1078 EP - 1091 ER - TY - GEN A1 - Adelmann, Christoph A1 - Schram, Tom A1 - Chew, Soon Aik A1 - Woicik, J. C. A1 - Brizzi, Simone A1 - Tallarida, Massimo A1 - Schmeißer, Dieter A1 - Horiguchi, Naoto A1 - Elshocht, Sven van A1 - Ragnarsson, Lars-Åke T1 - On the scalability of doped hafnia thin films T2 - Applied Physics Letters N2 - The scaling behavior of Gd- and Al-doped HfO2 films as gate dielectrics in metal-oxide-semiconductor (MOS) capacitors was studied. For equivalent oxide thicknesses (EOTs) in the range of 10 Å, crystallized Gd:HfO2 showed higher leakage current densities than crystallized Al:HfO2, with undoped HfO2 in between. Ultimately, the scalability of Al:HfO2 was limited by the ability to crystallize the films at a given thermal budget. As a result, for post-deposition annealing at 800 °C, the EOT of Al:HfO2 based MOS capacitors was limited to ∼8 Å. However, for such an EOT, leakage current densities were reduced by about 100× with respect to HfO2. This demonstrates the high potential of Al:HfO2 for low-standby-power MOS devices. KW - scalability KW - hafnia thin films KW - Al:HfO2 KW - Gd:HfO2 KW - EXAFS KW - equivalent oxide thickness (EOT) KW - leakage current KW - X-ray absorption spectroscopy (XAS) Y1 - 2014 U6 - https://doi.org/10.1063/1.4870075 SN - 0003-6951 SN - 1077-3118 IS - 104 SP - 122906-1 EP - 122906-4 ER - TY - GEN A1 - Nourbakhsh, Amirhasan A1 - Adelmann, Christoph A1 - Song, Yi A1 - Lee, Chang Seung A1 - Asselberghs, Inge A1 - Huyghebaert, Cedric A1 - Brizzi, Simone A1 - Tallarida, Massimo A1 - Schmeißer, Dieter A1 - Elshocht, Sven van A1 - Heyns, Marc A1 - Kong, Jing A1 - Palacios, Tomás A1 - De Gendt, Stefan T1 - Graphene oxide monolayers as atomically thin seeding layers for atomic layer deposition of metal oxides T2 - Nanoscale N2 - Graphene oxide (GO) was explored as an atomically-thin transferable seed layer for the atomic layer deposition (ALD) of dielectric materials on any substrate of choice. This approach does not require specific chemical groups on the target surface to initiate ALD. This establishes GO as a unique interface which enables the growth of dielectric materials on a wide range of substrate materials and opens up numerous prospects for applications. In this work, a mild oxygen plasma treatment was used to oxidize graphene monolayers with well-controlled and tunable density of epoxide functional groups. This was confirmed by synchrotron-radiation photoelectron spectroscopy. In addition, density functional theory calculations were carried out on representative epoxidized graphene monolayer models to correlate the capacitive properties of GO with its electronic structure. Capacitance–voltage measurements showed that the capacitive behavior of Al2O3/GO depends on the oxidation level of GO. Finally, GO was successfully used as an ALD seed layer for the deposition of Al2O3 on chemically inert single layer graphene, resulting in high performance top-gated field-effect transistors. KW - Graphene Oxide KW - seed layer KW - atomic layer deposition KW - oxygen plasma treatment KW - photoelectron spectroscopy KW - density functional theory KW - capacitance-voltage Y1 - 2015 U6 - https://doi.org/10.1039/C5NR01128K SN - 2040-3364 SN - 2040-3372 VL - 2015 IS - 7 SP - 10781 EP - 10789 ER - TY - CHAP A1 - Brizzi, Simone A1 - Tallarida, Massimo A1 - Adelmann, Christoph A1 - Ragnarsson, Lars-Åke A1 - Elshocht, Sven van A1 - Schmeißer, Dieter T1 - Structural changes in HfO2 thin films: thickness and doping dependence T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - In this work we show results regarding MOCVD and ALD HfO2 as well as Al-doped HfO2. We use Synchrotron Radiation Photoemission Spectroscopy (SRPES) to determine Hf/O atomic ratios and X-ray Absorption Spectroscopy (XAS) to investigate the electronic properties related to their crystallization. MOCVD films are synthesized at temperatures ranging from ambient to 400∘C and show structures from completely amorphous to monoclinic. ALD films are amorphous as deposited, and can crystallize after post-deposition anneal depending on the percentage of Al-doping. We discuss PES results in order to determine how close to stoichiometry the Hf/O atomic ratios of the films are, as well as the doping level. From XAS data, instead, we can point out how orbital hybridizations are related to structural and physical properties. KW - Structure KW - HfO2 thin films KW - thickness dependence KW - doping dependence KW - atomic layer deposition (ALD) Y1 - 2014 UR - http://www.dpg-verhandlungen.de/year/2014/conference/dresden/part/ds/session/49/contribution/9?lang=en SN - 0420-0195 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Cuypers, Daniel A1 - Fleischmann, Claudia A1 - Dorp, Dennis H. von A1 - Brizzi, Simone A1 - Tallarida, Massimo A1 - Müller, Matthias A1 - Hönicke, Philipp A1 - Billen, Arne A1 - Chintala, Ravi A1 - Conard, Thierry A1 - Schmeißer, Dieter A1 - Vandervorst, Wilfried A1 - Elshocht, Sven van A1 - Armini, Silvia A1 - De Gendt, Stefan A1 - Adelmann, Christoph T1 - Sacrificial Self-Assembled Monolayers for the Passivation of GaAs(100) Surfaces and Interfaces T2 - Chemistry of Materials N2 - The use of sacrificial self-assembled monolayers (SAMs) to prepare clean n-type GaAs (100) surfaces without band bending in vacuo is demonstrated. GaAs surface passivation using octadecanethiol SAMs after HCl cleaning is shown to lead to an enhancement of the room-temperature photoluminescence intensity. Synchrotron-radiation photoelectron spectroscopy (SRPES) finds that the interfacial oxide between GaAs and the SAM remains below the detection limit. Evidence for both Ga–S and As–S bonds at the GaAs–thiolate interface is found. The limited thermal stability of the SAM allows the desorption of the alkyl chains by in situ thermal annealing at temperatures above 180 °C, leaving S bonded to Ga behind. The resulting surface contains only a very small amount of O (0.05 ML coverage) and C (about 3% of the SAM remaining) and shows no band bending with the surface Fermi level close to the conduction band. Atomic layer deposition of Al₂O₃ on this surface occurs via the formation of Al–S bonds without introducing any additional band bending. This indicates that the surface preparation of n-type GaAs (100) using sacrificial octadecanethiol SAMs followed by in situ thermal removal provides a route toward GaAs/oxide interfaces without interfacial oxides and without band bending. KW - GaAs KW - passivation KW - Al₂O₃ KW - atomic layer deposition (ALD) KW - Synchrotron-radiation photoelectron spectroscopy (SRPES) KW - self assembled monolayers (SAM) KW - interface engineering Y1 - 2016 U6 - https://doi.org/10.1021/acs.chemmater.6b01732 SN - 0897-4756 SN - 1520-5002 VL - 28 IS - 16 SP - 5689 EP - 5701 ER -