ISBN 9783843950121

978-3-8439-5012-1, Reihe Physikalische Chemie

Maximilian Schwarz
Fabrication and Electrical Transport Properties of Silver Selenide Nanowire Field-Effect Transistors Obtained via Cation Exchange

193 Seiten, Dissertation Universität Hamburg (2021), Softcover, A5

Zusammenfassung / Abstract

Nanowires have been proposed as building blocks for field-effect transistors, offering control over the transport characteristics by tuning the nanowire diameter. Employing cation exchange provides the ability to manipulate the material composition post-synthesis to additionally tune the transport properties. In order to exploit this approach to its full potential, an understanding of the reaction dynamics is desirable.

Here, electrical transport measurements were used to characterize nanowires during and after cation exchange from CdSe to Ag2Se. Obtaining nanowires from substrate-based, wet chemical solution-liquid-solid synthesis followed by contacting of individual nanowires using optical lithography allowed for facile fabrication of nanowire field-effect transistors with a variety of diameters. In combination with simulations of the capacitive coupling of the back gate to the nanowire, determination of transport properties was possible in terms of specific conductivity, field-effect mobility and carrier concentration for individual nanowires. It was found that cation exchange can be carried out after completed device fabrication, enabling versatile modification of the active channel as evident by a transition from insulating CdSe to Ag2Se exhibiting metal-like 3D diffusive transport. A specific conductivity corresponding to Ag2Se bulk conductivity independent of nanowire diameter was found. At temperatures of around 100 °C, a superionic transition characteristic for Ag2Se was observed, presenting a pronounced decrease in transition temperature compared to a value of 133 °C for the bulk. This was attributed to the high surface-to-volume ratio in combination with the presence of phase boundaries in nanowires.

Results presented here provide a pathway for facile investigation of various material compositions by using nanowires that can be grown with a high degree of synthetic control as a template for cation exchange.