# Revealing a Pathway for Low‐Temperature Recrystallization in Germanium

## TL;DR

This paper shows that damaged germanium can be restored at room temperature using ionizing radiation, avoiding the need for high heat.

## Contribution

A nonthermal pathway for structural restoration in germanium is demonstrated using ionization-induced recovery.

## Key findings

- Energy transfer of 2.4 keV nm−1 from ions can annihilate defects in germanium at room temperature.
- The irradiation-induced crystalline-to-amorphous transformation in germanium is reversible without additional thermal energy.
- Recovery in preamorphized germanium starts outside the amorphous layer and reduces damage exponentially with fluence.

## Abstract

Thermally activated annealing in semiconductors faces inherent limitations, such as dopant diffusion. Here, a nonthermal pathway is demonstrated for a complete structural restoration in predamaged germanium via ionization‐induced recovery. By combining experiments and modeling, this study reveals that the energy transfer of only 2.4 keV nm−1 from incident ions to target electrons can effectively annihilate pre‐existing defects and restore the original crystalline structure at room temperature. Moreover, it is revealed that the irradiation‐induced crystalline‐to‐amorphous (c/a) transformation in Ge is reversible, a phenomenon previously considered unattainable without additional thermal energy imposed during irradiation. For partially damaged Ge, the overall damage fraction decreases exponentially with increasing fluence. Surprisingly, the recovery process in preamorphized Ge starts with defect recovery outside the amorphous layer and a shrinkage of the amorphous thickness. After this initial stage, the remaining damage decreases slowly with increasing fluence, but full restoration of the pristine state is not achieved. These differences in recovery are interpreted in the framework of structural differences in the initial defective layers that affect recovery kinetics. This study provides new insights on reversing the c/a transformation in Ge using highly‐ionizing irradiation and has broad implications across materials science, radiation damage mitigation, and fabrication of Ge‐based devices.

This study reports the discovery that energy transferred to electrons and atoms by highly ionizing ions results in a disorder‐order (amorphous‐crystalline) phase transformation in noncrystalline (amorphous) Ge. This discovery unlocks low‐temperature recrystallization pathways in Ge, offering a nonthermal strategy for fabricating Ge‐based devices that are temperature‐sensitive.