Low-temperature growth of self-organized ZnO nanorods on Si substrate is achieved using anodic aluminum oxide and atomic layer deposition at 250°C without catalyst or seed layer. Photoluminescence spectrum indicates that the ZnO nanorod arrays exhibit a blue/green luminescence at 480 nm. In addition, the nanorod arrays demonstrate excellent field-emission properties with a turn-on electric field of 6.5 V m −1 and a threshold electric field of 9.8 V m −1 , which are attributed to the perfectly perpendicular alignment of ZnO nanorods to the Si substrate.

This paper investigates the electromigration-induced failures of SnAg3.8Cu0.7 flip-chip solder joints. An under-bump metallization (UBM) of a Ti/Cr-Cu/Cu trilayer was deposited on the chip side, and a Cu/Ni(P)/Au pad was deposited on the BT board side. Electromigration damages were observed in the bumps under a current density of 2 ϫ 10 4 A/cm 2 and 1 ϫ 10 4 A/cm 2 at 100°C and 150°C. The failures were found to be at the cathode/chip side, and the current crowding effect played an important role in the failures. Copper atoms were found to move in the direction of the electron flow to form intermetallic compounds (IMCs) at the interface of solder and pad metallization as a result of current stressing.

Fabrication of anodic aluminum oxide ͑AAO͒ on 4 in. glass substrate was demonstrated. Using unique structure with quadruple contacts as electrode support during anodization, we reported gradual transformation from opaque aluminum to transparent AAO over the entire substrate. In contrast, partial transformation was observed with typical single contact approach where growth of insulating AAO inhibited subsequent anodization by interrupting current flow from the contact point. Results from optical spectroscope revealed moderate reduction in transmittance after AAO formation. Successful development of large-area AAO on glass substrate opens up opportunities for AAO templated devices that require a large footprint.Recently, self-organized nanostructures and devices have received much attention because their unique properties demonstrate considerable potentials in many applications. 1,2 Several techniques are reported to fabricate desirable structures including atomic layer deposition, focused ion-beam etching, and scanning probe-based nanolithography. 3-5 Unfortunately, these approaches are relatively time-consuming, expensive, and in particular confined to substrates with a limited footprint. As a result, alternative methods that are simple and especially suited to large areas are being intensively pursued. One of the promising solutions is to use anodic aluminum oxide ͑AAO͒ as a template to construct the intended nanostructure. The AAO consists of a close-packed hexagonal array of nanopores. Its characteristics could be adjusted by varying process parameters such as operation voltage, temperature, as well as electrolyte type and concentration. 6,7 To date, AAOs with highly ordered pore arrays are routinely prepared with tailored pore diameter and channel length.Several studies have reported growth of AAO film by direct anodization of Al deposited on substrates such as silicon and glass. [8][9][10] This was achieved by successive depositions of conductive underlayer and Al, and followed by typical anodization treatments. The as-synthesized AAO film was then used as the template to develop one-dimensional nanostructures in various oxides and metals. 11,12 From the standpoint of device fabrication, AAO film in large area is always preferred. However, due to lab-scaled experiment, AAO film that has been prepared so far is still confined to a limited area. 13,14 We believe lack of research in large area AAO formation is limiting its implementation in device fabrication of commercial scale.Transparent glass substrate is widely used for applications in photoelectrochemistry and photocatalysis. Owing to its insulating nature, direct anodization of Al on large-area glass substrate presents a serious challenge. Previously, Chu et al. employed tin-doped indium oxide predeposited on the glass substrate as a conductive layer to facilitate complete AAO formation. 15 In contrast, Miney et al. evaporated Al directly on microscope glass slide and reported successful oxidation of Al to AAO. 16 In addition, they noticed a selflimiting...

Ordered arrays of Ta2O5 nanodots were prepared using anodic aluminum oxide (AAO) as a template to support localized oxidation of TaN. Films of TaN (50 nm) and Al (1.5 μm) were deposited successively on p-type Si wafers and followed by a two-step anodization process at 40 V using oxalic acid as the electrolyte. The first anodization promoted growth of irregular AAO from overlying Al film. After chemical etching, the second anodization was performed to develop well-organized AAO channels and initiate oxidation of underlying TaN film to form tantalum oxide nanodots at the AAO pore bottoms. X-ray photoelectron spectroscopy results confirmed the chemical nature of nanodots as stoichmetric Ta2O5. X-ray diffraction demonstrated the amorphous characteristic of Ta2O5. As shown in field-emission scanning electron microscopy and transmission electron results, the Ta2O5 nanodots exhibited a hillock structure 80 nm in diameter at the bottom and 50 nm in height. We also synthesized 30-nm nanodots by adjusting AAO formation electrochemistry. This demonstrates the general applicability of the AAO template method for nanodot synthesis from nitride to oxide at a desirable size.

Ordered carbon nanotube ͑CNT͒ arrays were synthesized within anodized aluminum oxide template by thermal decomposition of hydrocarbon precursor with hydrogen ambient at growth temperature as low as 500°C. Excess hydrogen in precursor mixture enables a steady supply of mobile hydrocarbon reactant which promotes facile solid-phase diffusion. The activation energy for CNT growth was determined to be 0.55 eV, a number smaller than 1.02 eV for similar precursor in nitrogen ambient. Moreover, CNTs grown in anodized aluminum oxide nanopores in this low temperature process were found to exhibit unusually high field-emission current of 100 mA/ cm 2 at 8 V/m.