Simulation of Functional Interfaces

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en Musso, Tiziana 2016-09-28T09:01:31Z 2016-09-28T09:01:31Z 2016
dc.identifier.isbn 978-952-60-7030-8 (electronic)
dc.identifier.isbn 978-952-60-7029-2 (printed)
dc.identifier.issn 1799-4942 (electronic)
dc.identifier.issn 1799-4934 (printed)
dc.identifier.issn 1799-4934 (ISSN-L)
dc.description.abstract Functional interfaces are of fundamental importance in nano-electronic and photonic devices. Particularly, the interface between oxides and semiconductors is crucial for the overall device performance. Therefore, the modeling of novel semiconductor/oxide interfaces is fundamental to develop future economical, efficient and reliable microelectronic devices In this thesis, I use molecular dynamics (MD) and density functional theory (DFT) simulations to investigate the oxide/semiconductor interface between different materials. I first investigate the Charge-Optimized Many-Body potential (COMB), an empirical potential with the aim of modeling novel interfaces with realistic features. The COMB potential has been implemented within Physic, a calculator in an object-based Python environment. COMB is found to have substantial shortcomings when describing small systems like silica and hafnia clusters, where the local bonding environment is different compared to the bulk. Other empirical potentials have been used to model silica under high pressure, highlighting the general limitations of this class of potentials. Second, I report on my DFT studies of interfaces between transition metal dichalcogenides (TMDC) monolayers and functionalized graphenes. The excellent physical and semiconducting properties of TMDCs monolayers make them promising materials for many applications, particularly electronic devices. In order to develop logic circuits based on TMDCs, it is necessary to fabricate both n- and p-type field effect transistors (FETs). While monolayer n-FETs have been widely reported, fabrication of p-FETs has been challenging. This is due to the difficulty in designing MoS2/metal contacts with low Schottky barrier heights relative to the valence band. The idea discussed in this thesis consists in inserting a functionalized graphene layer (graphene oxide or graphene fluoride) between the TMDC and the metal contact, in order to modify the work function of the TMDC. I show that in this way it is possible to obtain hole-transport based devices, opening the road for a new, more affordable design of CMOS (complementary metal-oxide-semiconductor) devices. Overall, my results highlight the importance of simulations in helping providing an understanding of experimental results. Limitations should be considered, as in the case of empirical potentials. Through DFT simulations I have conceived a new way to obtain hole-transport in MoS2-based FETs, contributing to the research in facing the continuous miniaturization of electronic devices. en
dc.format.extent 80 + app. 94
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher Aalto University en
dc.publisher Aalto-yliopisto fi
dc.relation.ispartofseries Aalto University publication series DOCTORAL DISSERTATIONS en
dc.relation.ispartofseries 191/2016
dc.relation.haspart [Publication 1]: Thomas N. Jensen, Kristoffer Meinander, Stig Helveg, Adam S. Foster, Sampo Kulju, Tiziana Musso, Jeppe V. Lauritsen. Atomic Structure of a Spinel-Like Transition Al2O3 (100) Surface. Physical review letters, 113, 10,106103, September 2014. DOI: 10.1103/PhysRevLett.113.106103
dc.relation.haspart [Publication 2]: T. Hynninen, L. Himanen, V. Parkkinen, T. Musso, J. Corander, A.S. Foster. An object oriented Python interface for atomistic simulations. Computer Physics Communications, 198,230-237, January 2016. DOI: 10.1016/j.cpc.2015.09.010
dc.relation.haspart [Publication 3]: Teemu Hynninen, Tiziana Musso, Adam S. Foster. Limitations of reactive atomistic potentials in describing defect structures in oxides. Modelling and Simulation in Materials Science and Engineering, 24,3,035022, March 2016. DOI: 10.1088/0965-0393/24/3/035022
dc.relation.haspart [Publication 4]: Tiziana Musso, Priyank V. Kumar, Adam S. Foster, Jeffrey C. Grossman. Graphene Oxide as a Promising Hole Injection Layer for MoS2-Based Electronic Devices. ACS nano, 8,11,11432-11439, November 2014. DOI: 10.1021/nn504507u
dc.relation.haspart [Publication 5]: Tiziana Musso, Priyank V. Kumar, Jeffrey C. Grossman and Adam S. Foster. Engineering efficient p-type TMD/metal contacts using fluoro-graphene as a buffer layer. Submitted to Advanced Electronic Materials, June 2016. DOI: 10.1016/j.mattod.2016.03.018
dc.subject.other Physics en
dc.title Simulation of Functional Interfaces en
dc.type G5 Artikkeliväitöskirja fi Perustieteiden korkeakoulu fi School of Science en
dc.contributor.department Teknillisen fysiikan laitos fi
dc.contributor.department Department of Applied Physics en
dc.subject.keyword DFT en
dc.subject.keyword MD en
dc.subject.keyword interfaces en
dc.subject.keyword COMB en
dc.subject.keyword potentials en
dc.subject.keyword TMDC en
dc.subject.keyword graphene oxide en
dc.subject.keyword graphene fluoride en
dc.identifier.urn URN:ISBN:978-952-60-7030-8
dc.type.dcmitype text en
dc.type.ontasot Doctoral dissertation (article-based) en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.contributor.supervisor Foster, Adam S., Prof., Aalto University, Department of Applied Physics, Finland
dc.opn McKenna, Keith, Prof., University of York, U.K.
dc.contributor.lab Surfaces and Interfaces at the Nanoscale (SIN) en
dc.rev Nordlund, Kai, Prof., University of Helsinki, Finland
dc.rev Giordano, Livia, Prof., University of Milan-Bicocca, Italy 2016-10-15

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