Mass spectrometry and in situ x-ray photoelectron spectroscopy investigations of organometallic species induced by the etching of germanium, antimony and selenium in a methane-based plasma

International audienceOrganometallic positive ions were identified in inductively coupled plasmas by means of mass spectrometry during the etching of Ge, Sb, Se materials. A preliminary study was focused on identifying M x H y + (M = Ge, Sb, Se) positive ion clusters during a H 2 /Ar etching process. The methane addition to the H 2 /Ar mixture generates CH x reactive neutral species. The latter react with the metalloids within gas phase to form M x C y H z + organometallic ions. In addition, the etching of Sb 2 Se 3 and Ge 19.5 Sb 17.8 Se 62.7 bulk targets forms mixed products via ion-molecule reactions as evidenced by the presence of SeSbC x H y + ion clusters. Changes in surface composition induced by the newly formed organometallic structures were investigated using in situ x-ray photoelectron spectroscopy. In the case of the Ge and Sb surfaces, (M)–M–C x environments broadened the Ge 2p 3/2 , Ge 3d, Sb 3d and Sb 4d spectra to higher values of binding energy. For the Se surface, only the hydrogen and methyl bonding could explain the important broadening of the Se 3d core level. It was found that the Ge 39 Se 61 thin film presents an induced (Ge)–Ge–Se entity on the Ge 2p 3/2 and Ge 3d core levels

Insights into the Charge Carrier Terahertz Mobility in Polyfluorenes from Large-Scale Atomistic Simulations and Time-Resolved Terahertz Spectroscopy

Multiscale atomistic simulations were used to. understand the factors that determine the charge carrier mobility spectrum obtained from time-resolved terahertz (THz) spectroscopy in conjugated polymers. The simulation approach combines classical molecular dynamics simulations of atomic structure, large-scale electronic structure calculations, and the evaluation of the THz mobility using Kubo's linear response formula. We found that THz radiation probes a single carrier hop at low temperatures and high frequencies, while the transport over somewhat longer distances is probed in the opposite cases. Our results indicate that charge carrier transport at THz frequencies is thermally activated but with a much smaller activation energy compared to the dc case. The shape of the real and imaginary part of the mobility spectral curve reveals the presence of above THz hopping rates that are relevant for charge carrier transport. Strong differences of the mobilities in the polymer and the corresponding monomer material are largely caused by stronger energetic disorder of the monomer material