Francesca Clemente

Bandgap opening in oxygen plasma-treated graphene

We report a change in the semimetallic nature of single-layer graphene after exposure to oxygen plasma. The resulting transition from semimetallic to semiconducting behavior appears to depend on the duration of the exposure to the plasma treatment. The observation is confirmed by electrical, photoluminescence and Raman spectroscopy measurements. We explain the opening of a bandgap in graphene in terms of functionalization of its pristine lattice with oxygen atoms. Ab initio calculations show more details about the interaction between carbon and oxygen atoms and the consequences on the optoelectronic properties, that is, on the extent of the bandgap opening upon increased functionalisation density.

Analysis and modeling of the high vacuum scanning spreading resistance microscopy nanocontact on silicon

Within this paper, the authors propose a refined high vacuum scanning spreading resistance microscopy (HV-SSRM) electromechanical nanocontact model based on experimental results as well as molecular dynamics (MD) simulation results. The formation under the tip of a nanometer-sized pocket of β-tin, a metastable metalliclike phase of silicon (also named Si-II), acting as a virtual probe is demonstrated. This gives a reasonable explanation for the superior SSRM spatial resolution as well as for the electrical properties at the Schottky-like SSRM contact. Moreover, the impact of the doping concentration on the plastic deformation of silicon for different species using micro-Raman combined with indentation experiments is studied. In order to elucidate the superior results of SSRM measurements when performed under high vacuum conditions, the impact of humidity on the mechanical deformation and Si-II formation is also analyzed using MD and SSRM experimental results.

Controlled III/V Nanowire Growth by Selective-Area Vapor-Phase Epitaxy

We report on the growth of surface-bound, vertically oriented one-dimensional III/V nanostructures, specifically GaAs and InAs nanowires, on lattice-matched and -mismatched substrates by selective-area vapor-phase epitaxy. Control of nanowire features and growth directions is achieved by tuning the growth conditions. Grown nanostructures are characterized by scanning and transmission electron microscopy, X-ray diffraction, and Raman spectroscopy.

Degradation of 248 nm Deep UV Photoresist by Ion Implantation

Wet processes are gaining a renewed interest for removal of high dose ion implanted photoresist (II-PR) in front-end-of-line semiconductor manufacturing because of their excellent selectivity towards the wafer substrate and gate materials. The selection of wet chemistries is supported by an insight into the resist degradation by ion implantation. In this work, different analytical techniques have been applied for in-depth characterization of the chemical changes in 248 nm DUV PR after arsenic implantation. A radical mechanism of resist degradation is proposed involving cross-linking and chain scission reactions. The cross-linking of the resist is dominant especially for high doses and energies. It leads to significant depletion of hydrogen and formation of carbon macroradicals that recombine to form C-C cross-linked crust. Moreover, formation of ab-unsaturated ketonic and/or quinonoid structures by cross-linking reactions is suggested. In addition, the dopant species may provide rigid points in the PR matrix by chemical bonding with the resist. For higher doses and energies further dehydrogenation occurs, which leads to formation of triple bonds in the crust. Different p-conjugated structures are formed in the crust by cross-linking and dehydrogenation reactions. No presence of amorphous carbon in the crust is revealed.

Raman scattered photon transmission through a single nanoslit

We demonstrate excitation and detection of Raman scattering of a silicon substrate through a 15 nm gold nanoslit. Along with the nanoslit, a plasmonic cavity is fabricated to optimize optical transmission through the slit. Using a polarization analysis we prove that the plasmons enhanced transmission is responsible for the detection of the Raman scattered photons of the silicon substrate through the nanoslit. The optical cavity between the nanoslit and the Si substrate further enhances this backward photon transmission. This opens up prospects for new tools for near-field Raman spectroscopy and sub-wavelength measurements.

The Challenges of Ge-Condensation Technique

In order to integrate Ge CMOS technology however, new techniques for manufacturing Ge substrates/channels are needed. From integration point of view it is more interesting to manufacture device-quality Ge on top of standard SOI substrates, since this could allow the combination with standard Si CMOS circuitry in the same IC. One possible way for the development of ultra thin, Ge-on-insulator layers (GeOI) for < 45 nm technology nodes is the oxidation at high temperature of SiGe layers, epitaxially grown on an SOI substrates. This fabrication method is called Ge condensation technique. The potential of Ge condensation process as a technique to manufacture thin Ge-on-Insulator layers has already been demonstrated by Takagi et al. but limited process details are available (1,2). Little is known about the mechanisms of the intermediate stages of the condensation process.