# Black Nickel Coating as a Broadband Terahertz to Deep-Ultraviolet Absorber

## TL;DR

A black nickel coating is developed to absorb a wide range of electromagnetic radiation from terahertz to deep-ultraviolet frequencies.

## Contribution

A scalable and cost-effective black nickel coating is introduced as a broadband absorber spanning THz to DUV frequencies.

## Key findings

- The b-Ni coating achieves over 95% absorptivity from 30 to 1500 THz.
- The coating is fabricated via electrodeposition and acid etching, simplifying production.
- It outperforms nanostructured metamaterials in scalability and ease of fabrication.

## Abstract

Broadband absorbers capable of attenuating electromagnetic
radiation
from terahertz (THz) to deep-ultraviolet (DUV) frequencies are critical
components in spectroscopy, imaging, sensor technology, and energy
harvesting systems. However, most conventional absorbers are limited
by their narrow operational bandwidth and often require complex or
costly nanostructuring. In this study, we present a black nickel (b-Ni)
coating fabricated via scalable electrodeposition onto copper substrates,
followed by controlled acid etching, as a cost-effective and robust
broadband absorber. The resulting b-Ni films, characterized by scanning
electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS),
demonstrate ultrabroadband absorption spanning from 30 to 1500 THz,
with absorptivity exceeding 95% throughout this range. Compared to
nanostructured metamaterials and moth-eye analogs, the b-Ni coating
offers significant advantages in fabrication simplicity and scalability.
This work positions chemically etched b-Ni coatings as a highly promising
material for large-area applications in spectral and imaging instrumentation,
including emerging systems operating within the THz frequency range.