Electrochemical reactions typically involve electron transfer between an electrode and a dissolved chemical species at a solid-electrode/liquid-electrolyte interface. Three broad classes of electrochemical applications may be identified: (1) synthesis (or destruction), in which an applied potential is used to bring about a desired chemical oxidation or reduction reaction; (2) analysis, in which the current/potential characteristics of an electrode are used to determine the type and concentration of a species; and (3) power generation. These broad types of applications require stable, conductive, chemically robust, and economical electrodes. Diamond electrodes, fabricated by chemical vapor deposition, provide electrochemists with an entirely new type of carbon electrode that meets these requirements for a wide range of applications.

The first reports of electrochemical studies using diamond were in the mid-1980s. During the past several years, the field has attracted increasing attention. This review summarizes the electrochemical properties of diamond that make it a unique electrode material and that distinguish it from conventional carbon electrodes.

An integrated substrate, consisting of more than one material or material structure, is highly desirable for optimizing performance of multiple-device types on a single chip or for growing high-quality heteroepitaxial films on compliant substrates. A typical integrated substrate contains a stack of thin layers of similar or dissimilar materials that are either amorphous, or poly- or single-crystalline with a variety of lattice constants or crystallographic orientations. Partially or fully processed device layers can also be transferred onto a desired substrate where the transferred device layer can be further processed on the opposite side of its original surface. In this article, we focus on issues related to layer transfer for material integration.

Layer transfer from a hydrogen (H)-implanted wafer onto a desired substrate by wafer bonding and layer splitting (the so-called “Smart-Cut®” method) is an attractive approach to prepare integrated materials, such as-silicon-on-insulator (SOI), SiC or GaAs on oxidized silicon, and Ge on glass.

Considering all materials, diamond has many superior properties such as elastic constant (hardness), thermal conductivity, transparency to optical visible light and x-rays, a wide-bandgap semiconductor, and negative electron affinity. These properties lead to various applications in many industries. Because of the recent successful development of vapor-phase-growth technology, large-area diamond is available at a low manufacturing cost. However the commercialization of diamond at this stage is limited to tools, speaker diaphragms, heatsinks, and optical windows. For each application, diamond utilization is limited.

In this article, three avenues on the road to commercialization of vapor-phase-grown diamond will be discussed. The categories appear in Table I with the properties of diamond and its applications. First, applications already commercialized are briefly reviewed, and the requirements for expanding their market are discussed. Second, the technologies and applications coming in the near term are introduced. Last, future candidate applications for diamond are introduced along with technical obstacles to be overcome.

Over the past decade or so, research in silicon-based heterostructures has evolved from a few seminal publications on the growth and physical properties of Si1−xGex heteroepitaxial layers to a technology currently entering large-scale commercial production for heterojunction bipolar transistors (HBTs). During this period, extensive work has taken place on the optoelectronic applications of Si/Si1−x Gex such as 1.3–1.55 μam detectors for optical communication, 2–12-μm infrared detectors for two-dimensional (2D) focal plane arrays for night vision and thermal imaging, and infrared emitters for chip-to-chip optical communication as well as waveguiding and modulators. The overall goal of this work has been to merge optoelectronic functionality with the very large-scale-integration and electronic signal processing capabilities of silicon to create a silicon-based “superchip.”