TY - GEN A1 - Henkel, Karsten A1 - Das, Chittaranjan A1 - Kot, Małgorzata A1 - Schmeißer, Dieter A1 - Naumann, Franziska A1 - Kärkkänen, Irina A1 - Gargouri, Hassan T1 - In-gap states in titanium dioxide and oxynitride atomic layer deposited films T2 - Journal of Vacuum Science and Technology: A N2 - Valence band (VB) spectra of titanium dioxide (TiO2) and oxynitride (TiOxNy) films prepared by different atomic layer deposition (ALD) processes are compared and related to electrical characterization [current–voltage (JV) and capacitance–voltage (CV)] results. By increasing the nitrogen amount in the TiO2 film, band-gap narrowing is observed. The band-gap decrease is related to the contribution of the nitrogen density of states, which induces defects within the band-gap and thus reduces its optical band-gap. In-gap states are found in the VB spectra at 1 eV below the Fermi energy in all investigated ALD samples, i.e., in TiO2 as well as in TiOxNy films. An exponential correlation between leakage current density and in-gap state intensity is derived by the combination of JV measurements and VB spectra, whereas the in-gap states seem to have no influence on hysteresis and fixed oxide charges found in the CV data. It is argued that the in-gap states in TiO2 and TiOxNy have an excitonic or polaronic origin. Both, band-gap narrowing and in-gap state intensity can be tuned by the ALD process selection and the variation of its parameters. KW - Titanium dioxide (TiO2) KW - Titanium oxynitrdie (TiON) KW - valence band spectra KW - in-gap states KW - band-gap narrowing KW - electrical characterization Y1 - 2017 U6 - https://doi.org/10.1116/1.4972247 SN - 0734-2101 SN - 1520-8559 VL - 35 IS - 1 SP - 01B135-1 EP - 01B135-8 ER - TY - GEN A1 - Kot, Małgorzata A1 - Henkel, Karsten A1 - Das, Chittaranjan A1 - Brizzi, Simone A1 - Kärkkänen, Irina A1 - Schneidewind, Jessica A1 - Naumann, Franziska A1 - Gargouri, Hassan A1 - Schmeißer, Dieter T1 - Analysis of titanium species in titanium oxynitride films prepared by plasma enhanced atomic layer deposition T2 - Surface and Coatings Technology N2 - A comparative study of thin titanium oxynitride (TiOxNy) films prepared by plasma enhanced atomic layer deposition using tetrakis(dimethylamino)titanium (TDMAT) and N2 plasma as well as titanium(IV)isopropoxide and NH3 plasma is reported. The comparison is based on the combination of Ti2p core level and valence band spectroscopy and current-voltage measurements. The TDMAT/N2 process delivers generally higher fractions of TiN and TiON within the Ti2p spectra of the films and stronger photoemissions within the bandgap as resolved in detail by high energy resolution synchrotron-based spectroscopy. In particular, it is shown that higher TiN contributions and in-gap emission intensities correlate strongly with increased leakage currents within the films and might be modified by the process parameters and precursor selection. KW - Titanium oxynitride KW - Plasma enhanced atomic layer deposition (PEALD) KW - ALD process parameters KW - Ti-N contributions KW - In-gap defect states KW - Leakage current Y1 - 2017 U6 - https://doi.org/10.1016/j.surfcoat.2016.11.094 SN - 0257-8972 SN - 1879-3347 VL - 324 SP - 586 EP - 593 ER - TY - GEN A1 - Sowińska, Małgorzata A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Kärkkänen, Irina A1 - Schneidewind, Jessica A1 - Naumann, Franziska A1 - Gruska, Bernd A1 - Gargouri, Hassan T1 - Plasma-enhanced atomic layer deposition of titanium oxynitrides films: A comparative spectroscopic and electrical study T2 - Journal of Vacuum Science and Technology A N2 - The process parameters’ impact of the plasma-enhanced atomic layer deposition (PE-ALD) method on the oxygen to nitrogen (O/N) ratio in titanium oxynitride (TiOxNy) films was studied. Titanium(IV)isopropoxide in combination with NH3 plasma and tetrakis(dimethylamino) titanium by applying N2 plasma processes were investigated. Samples were characterized by the in situ spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and electrical characterization (current–voltage: I-V and capacitance–voltage: C-V) methods. The O/N ratio in the TiOxNy films is found to be very sensitive for their electric properties such as conductivity, dielectric breakdown, and permittivity. Our results indicate that these PE-ALD film properties can be tuned, via the O/N ratio, by the selection of the process parameters and precursor/coreactant combination. KW - plasma enhanced atomic layer deposition KW - titanium oxynitride KW - X-ray photoelectron spectroscopy KW - ellipsometry KW - current-voltage KW - capacitance-voltage Y1 - 2016 U6 - https://doi.org/10.1116/1.4936227 SN - 0734-2101 SN - 1520-8559 IS - 34 SP - 01A127-1 EP - 01A127-9 ER - TY - GEN A1 - Sowinska, Małgorzata A1 - Brizzi, Simone A1 - Das, Chittaranjan A1 - Kärkkänen, Irina A1 - Schneidewind, Jessica A1 - Naumann, Franziska A1 - Gargouri, Hassan A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Analysis of nitrogen species in titanium oxynitride ALD films T2 - Applied Surface Science N2 - Titanium oxynitride films are prepared by plasma enhanced atomic layer deposition method using two different precursors and nitrogen sources. Synchrotron radiation-based X-ray photoelectron spectroscopy and X-ray absorption spectroscopy are used to characterize the nitrogen species incorporated within these films depending on the deposition parameters. It is found that nitrogen atoms in these films are differently bonded. In particular, it can be distinguished between Ti-ON and Ti-N bonding configurations and molecular nitrogen species caused by precursor fragments. KW - titanium oxynitride KW - X-ray photoelectron spectroscopy KW - X-ray absorption spectroscopy KW - ALD process parameters Y1 - 2016 U6 - https://doi.org/10.1016/j.apsusc.2016.02.096 SN - 0169-4332 SN - 1873-5584 VL - 381 SP - 42 EP - 47 ER - TY - GEN A1 - Das, Chittaranjan A1 - Henkel, Karsten A1 - Tallarida, Massimo A1 - Schmeißer, Dieter A1 - Gargouri, Hassan A1 - Kärkkänen, Irina A1 - Schneidewind, Jessica A1 - Gruska, Bernd A1 - Arens, Michael T1 - Thermal and plasma enhanced atomic layer deposition of TiO2: Comparison of spectroscopic and electric properties T2 - Journal of Vacuum Science and Technology A N2 - Titanium oxide (TiO2) deposited by atomic layer deposition (ALD) is used as a protective layer in photocatalytic water splitting system as well as a dielectric in resistive memory switching. The way ALD is performed (thermally or plasma-assisted) may change the growth rate as well as the electronic properties of the deposited films. In the present work, the authors verify the influence of the ALD mode on functional parameters, by comparing the growth rate and electronic properties of TiO2 films deposited by thermal (T-) and plasma-enhanced (PE-) ALD. The authors complete the study with the electrical characterization of selected samples by means of capacitance–voltage and current–voltage measurements. In all samples, the authors found a significant presence of Ti3+ states, with the lowest content in the PE-ALD grown TiO2 films. The observation of Ti3+ states was accompanied by the presence of in-gap states above the valence band maximum. For films thinner than 10 nm, the authors found also a strong leakage current. Also in this case, the PE-ALD films showed the weakest leakage currents, showing a correlation between the presence of Ti3+ states and leakage current density. KW - titanium oxide (TiO2) KW - atomic layer deposition KW - plasma enhanced atomic layer deposition KW - synchrotron radiation photoelectron spectroscopy (SR-PES) KW - x-ray absorption spectroscopy KW - capacitance-voltage (CV) KW - current-voltage (IV) KW - ellipsometry KW - in-gap states Y1 - 2015 U6 - https://doi.org/10.1116/1.4903938 SN - 1520-8559 SN - 0734-2101 VL - 2015 IS - 33 SP - 01A144-1 EP - 01A144-8 ER - TY - CHAP A1 - Henkel, Karsten A1 - Das, Chittaranjan A1 - Sowinska, Małgorzata A1 - Tallarida, Massimo A1 - Schmeißer, Dieter A1 - Gargouri, Hassan A1 - Kärkkänen, Irina A1 - Schneidewind, Jessica A1 - Gruska, Bernd A1 - Arens, Michael ED - Glück, B. K. ED - Schmidt, S. ED - Stein, E. ED - Raschke, Jörg-Uwe ED - Richter, H. T1 - Charakterisierung von TiO2-ALD-Schichten und deren Nutzung für die Passivierung von Si-Photokathoden T2 - Tagungsband Photovoltaik-Meeting: Anwendungen-Qualität-Perspektiven, Senftenberg, 15.04.2015 N2 - Wir berichten zunächst über den Einfluss der Methode der Atomlagenabscheidung auf die TiO2-Schichteigenschaften. Insbesondere wird der Zusammenhang zwischen Ti3+- sowie Interbandzuständen mit elektrischen Kennlinien und deren Einfluss auf funktionale Schichteigenschaften diskutiert. Anschließend werden Mikrostrukturierung, Grenzflächen-Engineering und konforme Abscheidung einer TiO2-ALD-Schutzschicht effektiv zur Performance-Steigerung von p-Si-Photokathoden angewendet. KW - TiO2 KW - Korrosion KW - Atomlagenabscheidung KW - Silizium KW - Photokathoden KW - Linear Scan Voltametry KW - Photoelektronenspektroskopie Y1 - 2015 SP - 3 EP - 8 PB - BTU Cottbus-Senftenberg CY - Senftenberg ER -