Since the mid 1970's, quantum structures have attracted wide attention because of their potential in advanced device applications, such as planar superlattices field-effect transistors (FETs), quantum wire FETs, and quantum wire/quantum dot lasers [1]. Current techniques for preparation of low-dimensional devices present technical difficulties and concomitant costs. This is especially true in the fabrication of aligned quantum wire arrays. Microporous crystalline titanosilicate materials, ETS-4 and ETS-10, are hypothesized to have naturally occurring quantum wires in their framework [2]. They contain monatomic titania chains (…Ti-O-Ti-O-Ti...) isolated from each other by a highly siliceous matrix. These titania chains (~ 7 A in diameter) in ETS-4 run in only the b direction, while they run in both a and c directions in ETS-10.

Large ETS-4 and ETS-10 crystals have been synthesized to test their potential as quantum wire arrays [2]. Device integration of ETS-4 was performed utilizing the microfabrication methods including photolithography, metal deposition and etching. Current-voltage curves of these simple circuits were obtained at both ambient temperature and lower temperatures, varying in the range of 15-194 °K. Current versus voltage (I-V) curves of these devices exhibited a “square law” dependence which is consistent with the single electron transfer reported for nanoclusters [3]. Also, conduction through monatomic titania chains decreases with decreasing temperature which is consistent with both semiconductor behavior and tunneling effects where the probability of tunneling decreases with the decreasing temperature. The characteristic “stepwise” behavior of a single quantum wire was not observed, and was hypothesized to be due to the large number and distribution of chain lengths of titania in the framework of the crystal tested. In order to try an observe this stepped behavior, crystals have been tested by utilizing Scanning Tunneling Microscopy which makes it possible to obtain I-V curves for only few number of chains. These results taken in total provide some basis for utilizing ETS compounds in the manufacture optoelectronic devices.

[1] Akiyama Y, Sakaki H, Applied Physics Letters, 89, 183108, 2006

[2] Yilmaz B, Warzywoda J, Sacco A Jr, Journal of Crystal Growth, 271, 325-331, 2004.

[3] Feldheim D L, Grabar, K C, Natan M J, T E Mallouk, J. Am. Chem. Soc., Vol 118, No. 32, 1996