CRC 951/2: HIOS – Surface-Selective Functionalization of Inorganic Semiconductors (SP A08)

During the past funding period, we have learned how to adjust the work function of ZnO surfaces in the interval ranging from 2.2 eV to 6.5 eV using dipolar organophosphonates and strong molecular donors/ acceptors, and we have acquired understanding of the underlying fundamental mechanisms. As a key parameter the doping level of the inorganic semiconductor was identified. Consequently, we will now expand the parameter space for tuning the HIOS energy level alignment by including controlled doping of the organic semiconductor as means to impact interface energetics, which can be exploited in application-oriented CRC projects, particularly A11 (Christiansen), B3 (Blumstengel), B7 (Neher), and B13 (List-Kratochvil).
Furthermore, we have succeeded in optimising the HIOS energy levels for energy transfer. However, the full tunability, which would ideally cover the entire range of type-II situations (including type-I midway) across the energy gaps of inorganic and organic component, is not achievable when doping of one component induces Fermi-level pinning. Consequently, adjusting doping in both components must be achieved to exploit the full potential of HIOS. To this end, we plan to expand the inorganic semiconductors to be studied to GaN and Si, where p- and n-type doping is feasible. This opens the possibility to reach novel HIOS interface phenomena, and we will target realizing rather extreme HIOS interface energy levels, i.e., contact-induced inversion layer formation, which may be exploited towards (i) interfacial charge transfer and (ii) minority carrier charge injection in highly doped inorganic and organic semiconductors.
Additional efforts will be directed at (i) exploring to what extent non-symmetric dipolar molecules can be used in conjunction with in-plane dipoles of the ZnO(101􀴤0) surface, by controlling the competition between dipoledipole, hydrogen-bonding, and screening van-der-Waals interactions. And (ii) how multi-functional selfassembled monolayers can be employed for switching interface electronic levels by an external stimulus, as well as (iii) we aim at investigating if, and if so to which extent, highly doped ZnO [from A05 (Henneberger)] with essentially metallic properties differs in terms of coupling with organic semiconductors and the resulting interfacial electronic structure.
To provide improved fundamental understanding of structural and electronic HIOS interface properties our experimental results will be compared to pertinent theoretical modelling, which will in part also guide our selection of organic compounds [A04 (Heimel), A07 (Klapp/Dzubiella), B04 (Körzdörfer/Scheffler/Rinke)].

Principal investigators
Koch, Norbert Prof. Dr. techn. (Details) (Structure, Dynamics and electronic Properties of Molecular Systems)

DFG: Sonderforschungsbereich

Duration of project
Start date: 07/2015
End date: 06/2019

Research Areas
Experimental Condensed Matter Physics

Research Areas
Experimentelle Physik, kondensierte Materie

T. Schultz, R. Schlesinger, J. Niederhausen, F. Henneberger, S. Sadofev, S. Blumstengel,
A. Vollmer, F. Bussolotti, J.-P. Yang, S. Kera, K. Parvez, N. Ueno, K. Müllen, N. Koch,
“Tuning the work function of GaN with organic molecular acceptors”, Phys. Rev. B 93, 125309 (2016).

T. Schultz, J. Niederhausen, R. Schlesinger, S. Sadofev, N. Koch, “Impact of surface states and
bulk doping level on hybrid inorganic/organic semiconductor interface energy levels”,
J. Appl. Phys. 123, 245501 (2018).

R. Wang, T. Katase, K.-K. Fu, T. Zhai, J. Yang, Q. Wang, H. Ohta, N Koch, S. Duhm, “Oxygen vacancies
allow tuning the work function of vanadium dioxide”, Adv. Mater. Interfaces 5, 1801033 (2018).

K.-K. Fu, R. Wang, T. Katase, H. Ohta, N. Koch, S. Duhm, “Stoichiometric and oxygen-deficient VO2
as versatile hole injection electrode for organic semiconductors”,
ACS Appl. Mater. Interfaces 10, 10552 (2018).

M. H. Futscher, T. Schultz, J. Frisch, M. Ralaiarisoa, E. Metwalli, M. V. Nardi, P. Müller-Buschbaum,
N. Koch, “Electronic properties of hybrid organic/inorganic semiconductor pn-junctions”,
J. Phys. Condens. Matter, in press, DOI:10.1088/1361-648X/aaf310 (2018).

Q. Wang, J. Frisch, M. Herder, S. Hecht, N. Koch, “Electronic properties of optically switchable
photochromic diarylethene molecules at the interface with organic semiconductors”,
ChemPhysChem 18, 722 (2017).

T. Mosciatti, M. G. del Rosso, M. Herder, J. Frisch, N. Koch, S. Hecht, E. Orgiu, P. Samorì,
“Light-modulation of the charge injection in a polymer thin-film transistor by functionalizing electrodes
with bi-stable photochromic self-assembled monolayers”, Adv. Mater. 28, 6606 (2016).

Q. Wang, G. Ligorio, V. Diez Cabanes, D. Cornil, B. Kobin, J. Hildebrandt, M. V. Nardi, M. Timpel,
S Hecht, J. Cornil, E. J. W. List-Kratochvil, N. Koch, “Dynamic photo-switching of electron energy levels
at hybrid ZnO/organic photochromic molecule junctions”, Adv. Funct. Mater. 28, 1800716 (2018).

Z. Song, T. Schultz, Z. Ding, B. Lei, C. Han, P. Amsalem, T. Lin, D. Chi, S. L. Wong, Y. J. Zheng,
M.-Y. Li, L.-J. Li, W. Chen, N. Koch, Y. L. Huang, A. T. S. Wee, “Electronic properties of a 1D
intrinsic/p-doped heterojunction in a 2D transition metal dichalcogenide semiconductor”,
ACS Nano 11, 9128 (2017).

S. Park, N. Mutz, T. Schultz, S. Blumstengel, A. Han, A. Aljarb, L.-J. Li, E. J. W. List-Kratochvil,
P. Amsalem, N. Koch, “Direct determination of monolayer MoS2 and WSe2 exciton binding energies
on insulating and metallic substrates”, 2D Mater. 5, 025003 (2018).

Last updated on 2022-19-11 at 04:05