In materials that conduct both electricity and heat, the thermal and electrical currents are coupled. This thermoelectric coupling can be used to construct devices that act as temperature sensors, heat pumps, refrigerators, or power generators. A temperature difference ΔT across any electrical conductor will generate a corresponding voltage difference ΔV The ratio ΔV/ΔT is defined as the Seebeck coefficient S after Thomas See-beck who first discovered the effect in 1823. Probably the most familiar use of this effect is the thermocouple in which the union of two dissimilar metals generates a voltage in response to an imposed temperature difference. Interestingly an electrical current I passing through the junction of two dissimilar conductors results in the absorption or release of heat in the vicinity of the junction depending on the direction of the current. The ability to heat or cool in this manner was first discovered by Peltier and explained by Lord Kelvin. The latter showed that the amount of heat produced (or absorbed) near the junction is given by ΠI = STI where Π is called the Peltier coefficient and T is the temperature. It is primarily this effect that makes thermoelectric (Peltier) refrigeration possible. Thermoelectric refrigerators and power generators are attractive for many applications as they have no moving parts (except electrons and holes), use no liquid refrigerant, and last indefinitely.

A central challenge to modern materials science is the rational design and synthesis of new materials possessing exceptional properties. Recent advances in first-principles modeling methods and the availability of increasingly powerful computational resources make this goal increasingly achievable. The strength of these modeling methods lies in their predictive ability. They are able to reproduce the crystal structures and elastic properties of a large class of materials to within 2–3% of experimental values and have predicted a number of phase transitions that have been verified experimentally.

Despite the power of these methods, the process of designing materials from first principles is not usually a straight-forward or simple one. It requires overcoming a number of obstacles, some of them quite formidable. First a calculable figure of merit that correlates well with the desired property must be identified. While this may be straightforward in some cases, in others—such as predicting the ability of a material to isolate radionuclides over million-year time scales—the process of reducing complex properties to a few calculable variables can be rather difficult. Next a promising chemical system and a realistic set of crystal structures must be selected. This is not trivial because predicting the structures that can crystallize in a given system can be exceedingly challenging. However a wide variety of methods are available to aid in the generation of promising structures — comparative crystallography, algorithms based upon the concepts of crystalline nets and close packing, modern alloy theory methods, and simulated annealing strategies being some examples.

The stability and precision of modern scanning-tunneling-microscope (STM) systems allow positioning of the tip on a subnanometer scale. This advancement has stimulated diverse efforts on surface modifications in the nanometer and even atomic range, as recently reviewed by Avouris. The lateral movement of individual adatoms and molecules in a controlled manner on solid surfaces and the construction of structures on a nanoscale were first demonstrated by Eigler and collaborators at 4 K. The reason for operating the STM at low temperatures (apart from increased stability and sensitivity of the STM setup itself) is the necessity to freeze the motion of single adsorbates, which are very often mobile at ambient temperatures. By selecting strongly bonded adsorbate/substrate combinations and large molecules, it was possible to extend the lateral manipulation technique even to room temperature. In the case of large molecules, not only their translational motion but also internal flexure of the molecule during the positioning process must be considered. In general, different physical and chemical interaction mechanisms between tip and sample can be exploited for atomic-scale manipulation. We will concentrate in the following on lateral manipulation where solely the forces that act on the adsorbate because of the proximity of the tip are used. This means that long-range van der Waals and short-range chemical forces can be used to move atoms or molecules along the surface. No bias voltage or tunneling current is necessary. Apart from this technique, additional advances using the effects caused by the electric field generated by the bias voltage between tip and sample and by the current flowing through the gap region can be used for atomic or molecular modification.

The science and technology of ferroelectric thin films is currently attracting worldwide attention because of its application to a new generation of novel devices. Prime, among these applications are nonvolatile ferroelectric random-access memories (NVFRAMs), which have high speed and extended endurance. The core of an NVFRAM is a capacitor with a ferroelectric film sandwiched between two electrode layers. The polarization of the ferroelectric layer in two possible opposite directions, upon application of an electric field between the two electrodes, provides the logic “1” and “0” states needed for binary-code memory. In spite of the advances in the science and technology of ferroelectric thin films and their integration into ferroelectric capacitors, some materials-related integration strategies as well as manufacturability issues have delayed commercialization of NVFRAMs. High-density memories require storage elements that approach submicron lateral dimensions. Thus, improved understanding of the materials properties and polarization phenomena is needed in conjunction with the development of new characterization tools that can enable such an understanding. For example, a fundamental issue in ferroelectric thin-film capacitors is the exact nature of the complex domain structure in the polarizable ferroelectric layer and its dynamics under high-speed switching conditions. The miniaturization of NVFRAMs requires understanding of granularity in polarization reversal dynamics, fatigue, and retention characteristics. In this respect, theoretical models and electrical measurements (e.g., polarization hysteresis loops and transient currents) have provided substantial insights into the nature of the switching processes. However, the models (phenomenological in nature) and the electrical measurements provide only a global or macroscopic view of the switching process.