# Transition from Surface to Hopping Conduction in Stacked Nonepitaxial Bi2Se3 Dual Thin Films

## TL;DR

This paper explores how stacking thin films of a topological insulator changes its electrical transport behavior from surface-dominated to hopping conduction.

## Contribution

A new method for stacking nonepitaxial Bi2Se3 thin films is developed, revealing disorder-driven transport transitions.

## Key findings

- Single Bi2Se3 thin films show surface-dominated transport near 130 K.
- Dual thin-film stacks exhibit a resistance minimum at 50 K and hopping conduction.
- Magnetotransport measurements indicate disrupted surface coherence due to stacking.

## Abstract

We investigate quantum transport in topological insulators
through
nonepitaxial thin film stacking. A KOH­(potassium hydroxide)-assisted
mechanical transfer is developed for fabricating stacked nonepitaxial
Bi2Se3 dual thin films. While deliberate rotational
misalignment is introduced during stacking, X-ray diffraction confirms
the preservation of crystallinity and strong c-axis
orientation. Single thin-film samples exhibit a metallic-to-activated
transition near 130 K, indicative of surface-dominated transport.
In contrast, the dual thin-film stack shows a nonmonotonic resistance
minimum at 50 K, followed by an upturn well described by a three-dimensional
variable-range hopping model (R
2 ≈
0.98), suggesting disorder-driven localization. Magnetotransport measurements
further reveal suppressed linear magnetoresistance and enhanced weak
antilocalization, indicating disrupted surface coherence due to interfacial
hybridization. These results demonstrate that stacking-induced disorder
fundamentally alters the transport regime, favoring hopping conduction
over coherent surface states. This work provides a platform for engineering
quantum transport through nonepitaxial stacking in topological systems.