Axis dependent conduction polarity in the air-stable semiconductor, PdSe₂

Area of Science:

• Solid State Physics
• Materials Science
• Semiconductor Physics

Background:

• Axis-dependent conduction polarity (ADCP) is a rare electronic phenomenon where charge carrier type (p-type or n-type) varies with crystal orientation.
• Most known ADCP materials are metals, with few semiconductors exhibiting this effect, limiting its practical applications.

Purpose of the Study:

• To establish palladium diselenide (PdSe2) as a stable semiconductor exhibiting ADCP.
• To investigate the transport properties and underlying mechanisms of ADCP in doped PdSe2 crystals.

Main Methods:

• Growth and characterization of Ir-doped (p-type) and Sb-doped (n-type) PdSe2 crystals.
• Measurement of transport properties, including conductivity and thermopower, across various temperature ranges and doping levels.
• Density functional theory (DFT) calculations to elucidate the origin of ADCP.

Main Results:

• PdSe2, a stable semiconductor, demonstrates ADCP with electron-doped samples showing p-type conduction cross-plane and n-type conduction in-plane above 100-200 K.
• P-doped PdSe2 exhibits temperature-dependent thermopower, with in-plane thermopower becoming negative above ~360 K.
• DFT calculations confirm that effective mass anisotropy in valence and conduction bands drives ADCP in PdSe2.

Conclusions:

• PdSe2 is a promising stable semiconductor material for realizing ADCP.
• The observed ADCP in PdSe2 arises from inherent band structure properties, enabling directional charge transport.
• This discovery opens avenues for novel electronic devices and technologies utilizing directional charge migration.