This paper reviews the development, history, theoretical basis, and experimental performance of solid-state hydrogen detectors under flow-through conditions available to date such as pyroelectric, piezoelectric, fiber optic, and electrochemical devices. Semiconductor hydrogen detectors will only be reviewed briefly, as excellent reviews on this subject already exist. In view of the fact that almost all the devices that will be discussed later in this paper use Pd as a hydrogen trap, we devote a subsection to examining the role of palladium as a catalyst as well as some of the characteristics of the Pd-H z system. Non-solid-state hydrogen sensors, such as the flame ionization detector are not the object of this review. A useful feature of this review is a comparison of operating characteristics of each device in a general table in Sec. VII. In that section a general discussion is presented, including a critical comparison of the capabilities and parameters of various solid-state hydrogen sensors in the form of a table showing data collected from the literature. The Pd-fiber optic sensor is the most sensitive optical device operating at room temperature. The Pd-photopyroelectric sensor appears to be most economical and second best in sensitivity at room temperature; it has the best potential for high signal-to-noise operation at the widest temperature range, down to cryogenic temperatures. The Pd-field effect transistor devices exhibit the second highest sensitivity at elevated temperatures.

A quantitative analysis of linear temperature-dependent coupled thermoelectronic diffusion waves in the generation of the laserinduced IR photothermal radiometric signal from a photoexcited, plasmawave-dominated, semi-infinite semiconductor Si wafer is presented. The strong coupling between the (usually assumed decoupled) carrier and thermal wave transport equations is accounted for explicitly and the range of violation of the Vasil'ev-Sandomirskii condition is studied. Thermoelectronic coupling is found to degrade the sensitivity of the plasmaoriginating IR radiometric signal in high-quality process Si substrates at elevated background temperatures and high modulation frequencies, with the exception of highly degenerate plasmas.

Graphene nanoribbons (GNRs) have been suggested as a promising material for its use as nanoelectromechanical reasonators for highly sensitive force, mass, and charge detection. Therefore the accurate determination of the size-dependent elastic properties of GNRs is desirable for the design of graphene-based nanoelectromechanical devices. In this study we determine the size-dependent Young’s modulus and carbon-carbon binding energy in a homologous series of GNRs, C4n2+6n+2H6n+4 (n=2–12), with the use of all electron first principles computations. An unexpected linearity between the binding energy and Young’s modulus is observed, making possible the prediction of the size-dependent Young’s modulus of GNRs through a single point energy calculation of the GNR ground state. A quantitative-structure-property relationship is derived, which correlates Young’s modulus to the total energy and the number of carbon atoms within the ribbon. In the limit of extended graphene sheets we determine the value of Young’s modulus to be 1.09 TPa, in excellent agreement with experimental estimates derived for graphite and suspended graphene sheets.

Optically thin palladium metal films evaporated on different silicon based substrates are investigated following exposure to different concentrations of hydrogen gas in air. Laser modulated reflectance off the palladium surface of silicon oxide and silicon nitride substrates is used to recover information regarding the reflectivity inversion and α/β-phases of the palladium complex after both first and multiple gas cycling. Atomic force microscopy confirms the formation of metal nanostructures following exposure to hydrogen of the optically thin palladium films.

PbS quantum dots (QDs) of different sizes capped with short (NH4)3AsS3 inorganic ligands are produced via ligand exchange processes from oleate‐capped PbS QDs. The solid‐state photophysical properties of the control organic‐capped and the inorganic‐ligand‐capped QDs are investigated to determine their potential for optoelectronic applications. Ultrafast transient transmission shows that in the oleate‐capped QDs, carrier recombination at sub‐nanosecond scales occurs via Auger recombination, traps, and surface states. At longer times, intense signals associated with radiative recombination are obtained. After ligand exchange, the QDs become decorated with (NH4)3AsS3 complexes and relaxation is dominated by efficient carrier transfer to the ligand states on timescales as fast as ≈2 ps, which competes with carrier thermalization to the QD band edge states. Recombination channels present in the oleate‐capped QDs, such as radiative and Auger recombination, appear quenched in the inorganic‐capped QDs. Evidence of efficient carrier trapping at shallow ligand states, which appears more intense under excitation above the (NH4)3AsS3 gap, is provided. A detailed band diagram of the various relaxation and recombination processes is proposed that comprehensively describes the photophysics of the QD systems studied.