- Cadmium arsenide (Cd₃As₂) is an inorganic compound of cadmium and arsenic, where cadmium is in the +2 oxidation state and arsenic is present as the arsenide anion (As³⁻).
- It is a gray to black crystalline solid that belongs to the II–V semiconductor family, similar to cadmium phosphide. Structurally, Cd₃As₂ crystallizes in a tetragonal system at room temperature and exhibits a highly ordered arrangement that contributes to its unusual electronic behavior.
- In recent years, cadmium arsenide has gained significant attention as a three-dimensional Dirac semimetal, meaning it possesses electronic properties analogous to graphene but in a bulk material. This makes it a subject of intense research in condensed matter physics and materials science.
- Cadmium arsenide can be synthesized by directly reacting elemental cadmium and arsenic in a sealed, evacuated quartz ampoule at high temperatures (typically 500–800 °C) to prevent oxidation and loss of volatile arsenic. For thin-film applications, methods such as molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD) are used, allowing precise control over crystal quality and layer thickness. These techniques have enabled the exploration of Cd₃As₂ in nanostructures, thin films, and heterojunction devices.
- One of the most notable properties of Cd₃As₂ is its high electron mobility and low effective mass, which result in extremely fast charge transport. It has a direct bandgap near 0.5 eV in certain crystal orientations, but more importantly, its Dirac semimetal nature gives rise to linear energy-momentum dispersion in three dimensions. This leads to unique phenomena such as high-mobility transport, giant magnetoresistance, and potential topological surface states. These properties have made Cd₃As₂ a promising candidate for high-speed electronics, spintronics, quantum computing components, and advanced optoelectronic devices.
- Chemically, cadmium arsenide is stable in dry air at room temperature but decomposes when exposed to moisture or strong acids, releasing highly toxic arsine gas (AsH₃) according to the reaction:
- Cd₃As₂ + 6 H₂O → 3 Cd(OH)₂ + 2 AsH₃↑
- Arsine is acutely poisonous and potentially lethal even at very low concentrations, making strict inert-atmosphere handling and sealed storage essential. Cd₃As₂ is also sensitive to prolonged heating in air, which can lead to oxidation into cadmium oxide and arsenic oxides.
- From a safety perspective, cadmium arsenide is extremely hazardous because it combines the chronic toxicity of cadmium—a cumulative poison affecting the kidneys, bones, and lungs—with the acute toxicity of arsenic and arsine gas. Long-term exposure can lead to cancer and severe organ damage, while even short-term inhalation of arsine can be fatal. Consequently, Cd₃As₂ is handled only in specialized laboratories with rigorous containment systems, gloveboxes, and fume hoods.
- Environmentally, cadmium arsenide poses risks as a persistent source of heavy metal and metalloid contamination. Both cadmium and arsenic can bioaccumulate in plants, animals, and humans, causing ecological damage and long-lasting health effects. Any waste containing Cd₃As₂ is considered hazardous and must be disposed of under strict environmental regulations. Despite these dangers, the unique physical properties of cadmium arsenide continue to drive advanced research into next-generation semiconductor and quantum materials.
