Photoelectron spectromicroscopy at chalcopyrite films

Area of Science:

• Materials Science
• Surface Science
• Semiconductor Physics

Background:

• Copper indium diselenide (CuInSe₂) is a promising photovoltaic material.
• Understanding interfaces is crucial for optimizing thin-film solar cell performance.
• In situ deposition techniques allow for cleaner interfaces and better control.

Purpose of the Study:

• To investigate the interface properties between CuInSe₂ and subsequently deposited ZnSe/ZnO layers.
• To analyze the lateral homogeneity and diffusion effects at the interface.
• To characterize the impact of annealing on interface morphology and composition.

Main Methods:

• Molecular Beam Epitaxy (MBE) for CuInSe₂ film preparation.
• Metalorganic Molecular Beam Epitaxy (MOMBE) for in situ ZnSe and ZnO deposition.
• X-ray Photoelectron Spectroscopy (XPS), Low Energy Electron Diffraction (LEED), and Spectroscopic X-ray Photoelectron Emission Microscopy (XPEEM) for interface characterization.

Main Results:

• XPS and LEED confirmed the successful deposition of ZnSe and ZnO on CuInSe₂.
• Spectroscopic XPEEM revealed lateral inhomogeneities at the interface.
• In situ annealing induced significant lateral indium diffusion into the ZnSe/ZnO layers.

Conclusions:

• Annealing leads to detrimental In diffusion, affecting the uniformity of the CuInSe₂/ZnSe/ZnO heterostructure.
• Interface quality is compromised by In diffusion, potentially impacting device performance.
• Further strategies are needed to mitigate In diffusion for improved device stability.