(152f) Titanosillicates, Are They Natural Host for Quantum Wires?

To develop micro/nano optoelectronics, sustain miniaturization trends as well as develop photon/electron detectors at the cellular level, methods to produce quantum wire arrays are being evaluated. Quantum wire arrays are predicted to be superior when compared to quantum wells and quantum dots in that they have more prominent energy quantization effects, extremely high electron and photon mobility and are less temperature and are less polarization dependent than quantum wells. In addition, arrays ‘may’ allow some defects to be present and preserve device performance through electron tunneling.  An investigation was performed utilizing the natural occurring titania chains in titanosilicate materials (diameter ~ 7 Å, intrinsic quantum wires) to produce “quantum arrays”. A method to grow large (≥ 200 μm, ETS-4; ≥80 μm, ETS-10), oriented, reduced-defect crystals was developed. These crystals were incorporated into “microcircuits”, and current versus voltage (IV) curves were measure at 293 K, 194 K, 64 K, and 15 K. Results indicated a non-Ohmic behavior, which was not initially understood. Low temperature results showed higher resistance relative to 293 K, and the resistance saturated around 65 K. The IV curve at 15 K was found to be almost identical with that at 65 K. Additionally, in these initial tests, there appeared to be a hysteresis effect, which was determined to be due to structure breakdown due to resistance heating.  Two probe tests showed current peaks consistent with the theory of resonant tunneling for quantum superstructures, showing both rapidly increasing current peaks and negative differential resistances. Similar behavior has been observed on a metal-insulator-nanoparticle-insulator-metal (MINIM) capacitor. The observed IV curve was reported to be due to single electron traveling through each particle, suggesting by analogy possible quantum effects in ETS-4 and ETS-10. However, additional two probe tests using Zeolite A (NaA) and Zeolite Y (NaY) but without titania chains present showed similar IV behaviors. These findings suggest that quantum behavior does not dominate electron transport in ETS-10 and ETS-4, but rather the observed IV behavior likely occurs due to cation movement within the framework.