Material and optical characterizations have been conducted for epitaxially grown Ge1−xSnx thin films on Si with Sn composition up to 10%. A direct bandgap Ge0.9Sn0.1 alloy has been identified by temperature-dependent photoluminescence (PL) study based on the single peak spectrum and the narrow line-width. Room temperature PL emission as long as 2230 nm has also been observed from the same sample.

Fully strained and relaxed epitaxial Ge1-xSnx alloys with Sn contents up to 12 at. % have been grown on Ge buffered Si using an Epsilon® 2000 Plus commercial chemical vapor deposition system. Using a specialized growth approach intrinsic, p-type, and n-type alloys have been demonstrated. Material and optical characterization of these alloys indicate that the alloys are of high crystal quality in which the Sn is fully substitutional. Heterostructures of doped Ge/Ge1-xSnx/Ge have also grown to demonstrate their application in light emitting and detecting devices. Phosphorus doped Ge1-xSnx photoluminescence has also been observed at wavelengths up to 2.4 μm. Growth, materials and optical properties of these materials will be discussed.

Systems that are capable of robustly reproducing single-molecule junctions are an essential prerequisite for enabling the wide-spread testing of molecular electronic properties, the eventual application of molecular electronic devices, and the development of single-molecule based electrical and optical diagnostics. Here, a new approach is proposed for achieving a reliable single-molecule break junction system by using a microelectromechanical system device on a chip. It is demonstrated that the platform can (i) provide subnanometer mechanical resolution over a wide temperature range (≈77-300 K), (ii) provide mechanical stability on par with scanning tunneling microscopy and mechanically controllable break junction systems, and (iii) operate in a variety of environmental conditions. Given these fundamental device performance properties, the electrical characteristics of two standard molecules (hexane-dithiol and biphenyl-dithiol) at the singlemolecule level, and their stability in the junction at both room and cryogenic temperatures (≈77 K) are studied. One of the possible distinctive applications of the system is demonstrated, i.e., observing real-time Raman scattering in a single-molecule junction. This approach may pave a way to achieving high-throughput electrical characterization of single-molecule devices and provide a reliable platform for the convenient characterization and practical application of single-molecule electronic systems in the future.

This chapter outlines the main device platforms that are available for harnessing electric field-induced reactivity in a confined nanoscale gap. The chapter begins with an introduction that describes the general architecture of the available experimental platforms for the design of electrically driven molecular devices. It then discusses recent literature that demonstrate the interplay between the built-in local electric field in molecular systems (D-LEF) and the oriented external electric field (OEEF) of the device. The chapter concludes by describing a molecular device designed to specifically enhance molecular spectroscopy by utilizing OEEFs.

Two commonly observed charge transport mechanisms in single-molecule junctions are coherent tunneling and incoherent hopping. It has been generally believed that tunneling processes yield temperature-independent conductance behavior and hopping processes exhibit increasing conductance with increasing temperature. However, it has recently been proposed that tunneling can also yield temperature-dependent transport due to the thermal broadening of the Fermi energy of the contacts. In this work, we examine a series of rigid, planar furan oligomers that are free from a rotational internal degree of freedom to examine the temperature dependence of tunneling transport directly over a wide temperature range (78–300 K). Our results demonstrate conductance transition from a temperature-independent regime to a temperature-dependent regime. By examining various hopping and tunneling models and the correlation between the temperature dependence of conductance and molecular orbital energy offset from the Fermi level, we conclude thermally assisted tunneling is the dominant cause for the onset of temperature-dependent conductance in these systems.