The near ultraviolet spectroscopy and photodissociation dynamics of two families of asymmetrically substituted thiophenols (2- and 3-YPhSH, with Y = F and Me) have been investigated experimentally (by H (Rydberg) atom photofragment translational spectroscopy) and by ab initio electronic structure calculations. Photoexcitation in all cases populates the 11ππ* and/or 11πσ* excited states and results in S–H bond fission. Analyses of the experimentally obtained total kinetic energy release (TKER) spectra yield the respective parent S–H bond strengths, estimates of ΔE(A∼−X∼), the energy splitting between the ground (X∼) and first excited (A∼) states of the resulting 2-(3-)YPhS radicals, and reveal a clear propensity for excitation of the C–S in-plane bending vibration in the radical products. The companion theory highlights roles for both geometric (e.g., steric effects and intramolecular H-bonding) and electronic (i.e., π (resonance) and σ (inductive)) effects in determining the respective parent minimum energy geometries, and the observed substituent and position-dependent trends in S–H bond strength and ΔE(A∼−X∼). 2-FPhSH shows some clear spectroscopic and photophysical differences. Intramolecular H-bonding ensures that most 2-FPhSH molecules exist as the syn rotamer, for which the electronic structure calculations return a substantial barrier to tunnelling from the photoexcited 11ππ* state to the 11πσ* continuum. The 11ππ* ← S0 excitation spectrum of syn-2-FPhSH thus exhibits resolved vibronic structure, enabling photolysis studies with a greater parent state selectivity. Structure apparent in the TKER spectrum of the H + 2-FPhS products formed when exciting at the 11ππ* ← S0 origin is interpreted by assuming unintended photoexcitation of an overlapping resonance associated with syn-2-FPhSH(v33 = 1) molecules. The present data offer tantalising hints that such out-of-plane motion influences non-adiabatic coupling in the vicinity of a conical intersection (between the 11πσ* and ground state potentials at extended S–H bond lengths) and thus the electronic branching in the eventual radical products.

Hydrogen Silsesquioxane (HSQ) photoresist has shown extremely high-resolution performance for Electron-Beam Lithography (EBL) and Interference Lithography (IL) and can be a potential photoresist candidate for Extreme Ultraviolet Lithography (EUVL). To optimize this system for sub-10 nm patterning, it is important to understand the EUV and electron-induced chemistry underpinning the functionality of this resist material. Here we present a EUVprintability study on HSQ photoresist at a resolution of 16 and 22 nm combined with a mechanistic study on EUV and electron-induced desorption of HSQ film. Firstly, patterning results showed that the simple HSQ cages require a high EUV-dose and an aggressive developer to print dense features. EUV-and electron-induced desorption experiments revealed that hydrogen and silane are the dominant species fragmented from HSQ, indicating dehydrogenation and redistribution pathways as the crosslinking mechanism. Quantum chemical calculations suggested that the Neutral Dissociation (ND) is the dominant mechanism in HSQ cross-linking at low energies, i.e., below its ionization threshold, whereas Dissociative Ionization (DI) contributes significantly at higher energies. A distinct structure is observed at about 8 eV and a clear peak at about 11 eV indicating a significant contribution through Dissociative electron attachment (DEA) at these energies. Based on these results, an engineered HSQ system is designed by adding silanol or carbinol (R-CH3OH)-groups to the partially crosslinked HSQ-cages to increase its Tetramethylammonium hydroxide (TMAH)-developer and EUV-sensitivity. Finally, 2.38% v/v TMAH is used to develop a 16 nm printed dense line-space (L/S) with a line-edge-roughness (LER) of 6.4 nm but requiring an EUV-dose of over 100 mJ/cm 2 .

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Secondary electrons generated during the Extreme Ultraviolet Lithography (EUVL) process are predominantly responsible for inducing important patterning chemistry in the photoresist film. Therefore, it is crucial to understand the electron-induced...

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Platinum coordination complexes have found wide applications as chemotherapeutic anticancer drugs in synchronous combination with radiation (chemoradiation) as well as precursors in focused electron beam induced deposition (FEBID) for nano-scale fabrication. In both applications, low-energy electrons (LEE) play an important role with regard to the fragmentation pathways. In the former case, the high-energy radiation applied creates an abundance of reactive photo- and secondary electrons that determine the reaction paths of the respective radiation sensitizers. In the latter case, low-energy secondary electrons determine the deposition chemistry. In this contribution, we present a combined experimental and theoretical study on the role of LEE interactions in the fragmentation of the Pt(II) coordination compound cis-PtBr2(CO)2. We discuss our results in conjunction with the widely used cancer therapeutic Pt(II) coordination compound cis-Pt(NH3)2Cl2 (cisplatin) and the carbonyl analog Pt(CO)2Cl2, and we show that efficient CO loss through dissociative electron attachment dominates the reactivity of these carbonyl complexes with low-energy electrons, while halogen loss through DEA dominates the reactivity of cis-Pt(NH3)2Cl2.

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In chemoradiation therapy, dissociative electron attachment (DEA) may play an important role with respect to the efficiency of the radiosensitizers used. The rational tailoring of such radiosensitizers to be more susceptive to DEA may thus offer a path to increase their efficiency. Potentially, this may be achieved by tailoring rearrangement reactions into the DEA process such that these may proceed at low incident electron energies, where DEA is most effective. Favorably altering the orbital structure of the respective molecules through substitution is another path that may be taken to promote dissociation up on electron capture. Here we present a combined experimental and theoretical study on DEA in relation to pentafluorothiophenol (PFTP) and 2-fluorothiophenol (2-FTP). We investigate the thermochemistry and dynamics of neutral HF formation through DEA as means to lower the threshold for dissociation up on electron capture to these compounds, and we explore the influence of perfluorination on their orbital structure. Fragment ion yield curves are presented, and the thermochemical thresholds for the respective DEA processes are computed as well as the minimum energy paths for HF formation up on electron capture and the underlying orbital structure of the respective molecular anions. We show that perfluorination of the aromatic ring in these compounds plays an important role in enabling HF formation by further lowering the threshold for this process and through favorable influence on the orbital structure, such that DEA is promoted. We argue that this approach may offer a path for tailoring new and efficient radiosensitizers.