Frequency and amplitude stabilized terahertz quantum cascade laser as local oscillator

We demonstrate an experimental scheme to simultaneously stabilize the frequency and amplitude of a 3.5 THz third-order distributed feedback quantum cascade laser as a local oscillator. The frequency stabilization has been realized using a methanol absorption line, a power detector, and a proportional-integral-derivative (PID) loop. The amplitude...

In situ study of hydrogen silsesquioxane dissolution rate in salty and electrochemical developers

In order to better characterize the development of the electron-beam resist hydrogen silsesquioxane (HSQ), the authors used a quartz crystal microbalance (QCM) to study its rate of dissolution in situ. The authors determined the effect of both salt concentration and applied electric potential on the development rate of HSQ. The development rates...

Terahertz heterodyne spectrometer using a quantum cascade laser

A terahertz (THz) heterodyne spectrometer is demonstrated based on a quantum cascade laser (QCL) as a local oscillator (LO) and an NbN hot electron bolometer as a mixer, and it is used to measure high-resolution molecular spectral lines of methanol (CH3OH) between 2.913–2.918 THz. The spectral lines are taken from a gas cell containing methanol...

Atomic radical abatement of organic impurities from electron beam deposited metallic structures

Focused electron beam induced processing (FEBIP) of volatile organometallic precursors has become an effective and versatile method of fabricating metal-containing nanostructures. However, the electron stimulated decomposition process responsible for the growth of these nanostructures traps much of the organic content from the precursor’s ligand...

Roles of secondary electrons and sputtered atoms in ion-beam-induced deposition

The authors report the results of investigating two models for ion-beam-induced deposition (IBID). These models describe IBID in terms of the impact of secondary electrons and of sputtered atoms, respectively. The yields of deposition, sputtering, and secondary electron emission, as well as the energy spectra of the secondary electrons were...

Sub-10-nm nanolithography with a scanning helium beam

Scanning helium ion beam lithography is presented as a promising pattern definition technique for dense sub-10-nm structures. The powerful performance in terms of high resolution, high sensitivity, and a low proximity effect is demonstrated in a hydrogen silsesquioxane resist.

Influence of hydrogen silsesquioxane resist exposure temperature on ultrahigh resolution electron beam lithography

Performance of hydrogen silsesquioxane (HSQ) resist material with respect to the temperature during electron beam exposure was investigated. Electron beam exposure at elevated temperatures up to 90?°C shows sensitivity rise and slight contrast (?) degradation compared to lower temperature cases. Ultrahigh resolution structures formed at elevated...

Thermal and electrical properties of porphyrin derivatives and their relevance for molecule interferometry

The authors present new measurements of thermal and electrical properties for two porphyrin derivatives. They determine their sublimation enthalpy from the temperature dependence of the effusive beam intensity. The authors study H2TPP and Fe(TPP)Cl in matter-wave interferometry. Both molecules have nearly equal de Broglie wavelengths but...

Phonon driven proton transfer in crystals with short strong hydrogen bonds

Recent work on understanding why protons migrate with increasing temperature in short, strong hydrogen bonds is extended here to three more organic, crystalline systems. Inelastic neutron scattering and density functional theory based simulations are used to investigate structure, vibrations, and dynamics of these systems as functions of...

Intermolecular interactions in solid benzene

The lattice dynamics and molecular vibrations of benzene and deuterated benzene crystals are calculated from force constants derived from density-functional theory (DFT) calculations and compared with measured inelastic neutron-scattering spectra. A very small change (0.5%) in lattice parameter is required to obtain real lattice-mode frequencies...

Charge transport in columnar stacked triphenylenes: Effects of conformational fluctuations on charge transfer integrals and site energies

Values of charge transfer integrals, spatial overlap integrals and site energies involved in transport of positive charges along columnar stacked triphenylene derivatives are provided. These parameters were calculated directly as the matrix elements of the Kohn–Sham Hamiltonian, defined in terms of the molecular orbitals on individual...

Potential model for tetrathiafulvalene based on inelastic neutron scattering and Raman spectra

Tetrathiafulvalene (TTF) is a key molecule in the family of charge-transfer salts of interest for their novel transport properties. The correspondence between transport property and electron-molecular vibration coupling requires that we understand the phonon density of states for these materials. Here we report the results of a low temperature...

Theoretical and experimental studies of the opto-electronic properties of positively charged oligo(phenylene vinylene)s: Effects of chain length and alkoxy substitution

In this paper a combined experimental and quantum chemical study of the geometry and opto-electronic properties of unsubstituted and dialkoxy-sustituted phenylene–vinylene oligomers (PV’s) is presented. The optical absorption spectra for PV cations with different chain lengths and substitution patterns were measured using pulse radiolysis with...