Size and Shape Controlled Semiconductor Nanocrystals Synthesized by RF‐Sputtering Techniques for Electronic and Optoelectronic Applications

Abstract

AbstractGroup IV (Ge and Si) nanocrystals embedded in a dielectric matrix were prepared via rf magnetron sputtering by the deposition of superlattices of stoichiometric and substoichiometric oxide layers and subsequent annealing. By this way Ge nanocrystals in a (Ta)ZrOx and Si nanocrystals in an SiO2 matrix were prepared in a size and shape controlled manner. In case of the Ge‐ZrO2 system, elongated Ge nanocrystals in a crystallized ZrO2 matrix were formed for annealing temperatures above 660 °C. Starting from a Si3N4 interface of the Si wafer, a preferential orientation between the Ge and ZrO2 lattice can be stated. Doping the ZrO2 matrix additionally with Ta increases the crystallization temperature of the ZrO2 matrix and leads to the formation of Ge nanocrystals embedded in an amorphous TaZrOx matrix. The Ge nanocrystals were investigated by photoluminescence measurements and implemented into metal‐insulator‐semiconductor capacitor to investigate their potential for charge trapping devices. The prepared nano floating gate devices show good charging characteristics with a maximum memory window of 5 V and a slope of the writing voltage vs. memory window characteristics of 0.8‐1. All luminescence centers seen in the Ge‐(Ta)ZrOx system can be attributed to defects either from the Ge nanocrystal surface, the (Ta)ZrOx matrix or the Si substrate itself. Si nanocrystals were fabricated in the same way in an amorphous SiO2 film after annealing above 900 °C. The formed Si nanocrystals act as superior sensitizer for Er3+ ions which were ion implanted into the films followed by an additional subsequent anneal, varied between 700 and 1000 °C. The Si nanocrystal ‐ Er3+ system was successfully implemented into a slot waveguide structure showing a strong polarization dependent field enhancement in both emission and excitation geometry. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)