Ultraviolet antireflection coatings for use in silicon detector design

Area of Science:

• Optical engineering
• Detector physics
• Materials science

Background:

• Single-layer antireflection (AR) coatings are unsuitable for UV spectrographs due to silicon's variable refractive index.
• Optimizing quantum efficiency (QE) across a broad UV spectrum (120-300 nm) requires advanced coating solutions.

Purpose of the Study:

• To develop and test novel broadband AR coatings for CCD detectors used in UV spectrographs.
• To achieve theoretical QEs greater than 60% across the 120-300 nm wavelength range.

Main Methods:

• Coating backside-illuminated, thinned, delta-doped CCDs with multiple thin-film AR layers.
• Utilizing materials like MgF2, SiO2, Al2O3, MgO, and HfO2, each optimized for specific UV sub-bands.
• Testing various deposition techniques and selecting coatings that minimize reflectance on silicon test wafers.

Main Results:

• Demonstrated theoretical QEs exceeding 60% for CCD detectors between 120-300 nm.
• Identified optimal material combinations (e.g., MgF2 for 120-150 nm, HfO2 for 240-300 nm).
• Successfully applied selected coatings to functional CCD devices.

Conclusions:

• A multi-layer thin-film coating approach effectively enhances UV CCD detector QE.
• The developed coatings significantly improve performance for UV spectrographic applications.
• Future work includes exploring graded and multilayer coatings for further optimization.