Growth of Bi2Te3quantum dots/rods in glass: a unique highly stable nanosystem with novel functionality for high performance magneto optical devices

Abstract

Magneto optical materials are currently of great interest, primarily for modern applications in optical isolation, modulation and switching in telecommunication. However, single crystals are the benchmark materials still used in these devices which are rather expensive and very difficult to fabricate. In this context, we are reporting herewith a stable and novel Bi₂Te₃ quantum dot–glass nanosystem obtained using a controlled thermo-chemical method. The Q-dots of hexagonal Bi₂Te₃ of size 4 to 14 nm were grown along the 〈1 1 3〉 direction. Surprisingly, we obtained quantum rods of Bi₂Te₃ of size 6 × 10 nm for the first time. The strong quantum confinement in the nanosystem is clearly shown by the optical study. The band gap of the host glass was drastically reduced (from 4.00 to 1.88 eV) due to the growth of Bi₂Te₃ quantum dots whereas photoluminescence showed a Stokes shift ∼175 meV. Faraday Rotation (FR) investigations of the Bi₂Te₃ quantum dot–glass nanosystem show a nonlinear response in Verdet constant with a decrease in the Bi₂Te₃ dot sizes. The Bi₂Te₃ Q-dot–glass nanosystem with ∼4 nm dots shows significant enhancement (70 times) in Verdet constant compared to the host glass and more radically better than conventional single crystal (TGG). This is the first time that such a type of unique nanosystem has been architectured and has given extremely good magneto-optical performance. We strongly feel that this novel nanosystem has tremendous applications in magneto-optical devices. It is noteworthy that expensive single crystals can be replaced with this cost effective novel glass nanosystem. Interestingly, the present quantum dot–glass nanosystem can be transformed into optical fibers very easily, which will have an exceptionally high impact on the fabrication of high performance magneto optical devices.