Ultrafast Infrared Laser Crystallization of Amorphous Ge Films on Glass Substrates

Area of Science:

• Materials Science
• Nanotechnology
• Laser Physics

Background:

• Amorphous germanium (a-Ge) films are crucial for semiconductor applications.
• Controlling the crystallization of a-Ge is essential for advanced material properties.
• Laser annealing offers precise control over material transformations.

Purpose of the Study:

• To investigate the crystallization of amorphous germanium films using ultrashort near-infrared and mid-infrared laser pulses.
• To determine the effect of laser energy density (fluence) on germanium crystallization.
• To explore the potential for creating micro- and nanocrystalline germanium films on flexible substrates.

Main Methods:

• Annealing of amorphous germanium films on glass substrates using picosecond (1.4 ps, 1030 nm) and femtosecond (70 fs, 1500 nm) laser pulses.
• Irradiation at laser energy densities ranging from 25 to 400 mJ/cm² under single-shot and multishot conditions.
• Analysis of germanium crystallization using Raman spectroscopy with 785 nm laser excitation.

Main Results:

• Established the dependence of the crystalline phase fraction on laser fluence for both picosecond and femtosecond laser annealing.
• Achieved regimes of near-complete crystallization across the entire film thickness.
• Demonstrated the feasibility of scanning laser processing for germanium film fabrication.

Conclusions:

• Ultrashort laser pulses effectively crystallize amorphous germanium films.
• Tunable crystallization of germanium is achievable by controlling laser parameters and fluence.
• Scanning laser processing enables the fabrication of micro- and nanocrystalline germanium films on flexible substrates, opening possibilities for flexible electronics.