A broad overview of packaging involving interconnecting, powering, protecting, and cooling semiconductor chips to meet a variety of computer system needs is presented. The general requirements for ceramics in terms of their thermal, mechanical, electrical, and dimensional control requirements are presented, both for high-performance a n d lowperformance applications. Glassceramics are identified as the best candidates for high-performance systems, and aluminum nitride, alumina, or mullite are identified for lowperformance systems. Glass-ceramic/ copper substrate technology is discussed as an example of highperformance ceramic packaging for use in 1990s. Lower-dielectric-constant ceramics such as composites of silica, borosilicate, and cordierite, with or without polymers and porosity, are projected as potential ceramic substrate materials by the year 2000.[

Rectifying diodes of single nanobelt/nanowire-based devices have been fabricated by aligning single ZnO nanobelts/nanowires across paired Au electrodes using dielectrophoresis. A current of 0.5 µA at 1.5 V forward bias has been received, and the diode can bear an applied voltage of up to 10 V. The ideality factor of the diode is ∼3, and the on-to-off current ratio is as high as 2000. The detailed IV characteristics of the Schottky diodes have been investigated at low temperatures. The formation of the Schottky diodes is suggested due to the asymmetric contacts formed in the dielectrophoresis aligning process.Zinc oxide is an important optical and optoelectronic material. Recently, utilizing its unique crystal structure and the three major fastest growth directions, various singlecrystal/crystalline nanostructures of ZnO have been synthesized, such as nanobelts, 1 nanorings, 2 and nanohelices. 3 From the abundance of the surface morphologies, ZnO offers the most diverse nanostructure of any material known today. With a large direct band gap of 3.37 eV, together with its piezoelectricity and pyroelectricity, ZnO is most attractive for applications as a field-effect transistor (FET) 4 or sensor 5 and in optical electronics. 6 Extensive research on the electronic properties of various one-dimensional nanostructures has been performed. [7][8][9][10] To apply ZnO nanostructures on various electronic devices, it is important for one to understand its transport properties and its interaction with metal contacts. In this letter, we investigated the contact of a single ZnO nanobelt with gold electrodes. After investigating the transport properties of over 60 single nanobelt-based circuits, we found a spontaneous formation of a Au/ZnO nanobelt Schottky diode in 80% of the samples when nanobelt sizes are well controlled. This effect is likely due to the nonsymmetric contacts at the two ends of the nanobelt.The ZnO nanobelts to be used for fabricating the FET devices were synthesized through a solid-vapor process in a high-temperature horizontal furnace system. 1 The Au electrode patterns were defined with photolithography on a SiO 2 substrate. The electrodes consisted of two 3-µm-wide fingers pointed head to head at a distance of 4 µm. These two fingers are connected to two 500 × 500 µm 2 contacting pads for probe contacts. The as-synthesized nanobelt samples were placed in ethanol and ultrasonicated for 15 min to disperse the bundles into individual nanobelts. A single nanobelt is "placed" across the prefabricated electrodes using the dielectrophoresis technique. 11 After applying a droplet of the nanobelt suspension onto the electrodes, the electrodes were connected to a 5 V and 1 MHz AC signal, which was chosen for optimizing the alignment of a single nanobelt. This signal generated an alternating electrostatic force on the nanobelts in the solution. Under the electrical polarization force, the nanobelts were deposited on the electrodes. By precisely controlling the concentration of the nanobelt in the solution, ...

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By assembling a ZnO nanowire (NW) array based nanogenerator (NG) that is transparent to UV light, we have investigated the performance of the NG by tuning its carrier density and the characteristics of the Schottky barrier at the interface between the metal electrode and the NW. The formation of a Schottky diode at the interface is a must for the effective operation of the NG. UV light not only increases the carrier density in ZnO but also reduces the barrier height. A reduced barrier height greatly weakens the function of the barrier for preserving the piezoelectric potential in the NW for an extended period of time, resulting in little output current. An increased carrier density speeds up the rate at which the piezoelectric charges are screened/neutralized, but a very low carrier density prevents the flow of current through the NWs. Therefore, there is an optimum conductance of the NW for maximizing the output of the NG. Our study provides solid evidence to further prove the mechanism proposed for the piezoelectric NG and piezotronics. The output current density of the NG has been improved to 8.3 µA/cm 2 .Developing nanomaterial-enabled technologies for energy harvesting has attracted a lot of interest recently. 1,2 Using aligned ZnO nanowire (NW) arrays, we have recently demonstrated a nanogenerator (NG) for converting mechanical energy into electricity. 3,4 The mechanism of the NG relies on the coupled semiconducting and piezoelectric properties and is composed of two processes. 5,6 When a clean ZnO NW or nanobelt is bent by an atomic force microscope (AFM) tip, an asymmetric strain is produced across the width of the NW. As a result of piezoelectricity, the stretched side of the NW has a positive potential and its compressed side has a negative potential. The contact between a Pt coated tip with ZnO is a Schottky diode. When the tip contacts the NW and bends it, the contact between the tip and the stretched side is a reversely biased Schottky diode. In such a case, a piezoelectric potential is created in the NW, but there is no charge flowing across the Schottky diode although there is a piezoelectric potential in the NW side, resulting in a charge creation and accumulation. This is the first process. When the tip scans in contact mode and reaches the compressed side of the NW, a forward biased Schottky diode is formed at the interface; thus, the external electrons can flow across the interface under the driving of the piezoelectric potential, resulting in an external current detected by the measurement meter. This is the current output process.The mechanism of the NG is based on two important physical quantities. One is the height of the Schottky barrier, which needs to be high enough to hold the charges from leaking. Second, the conductivity and carrier density of the ZnO NW are adequately low in the first step to preserve the piezoelectric potential distribution in the NW from being "neutralized" by the freely flowing charge carriers, which are electrons for n-type ZnO, but they need to be high ...