Amorphous Transparent Cu(S,I) Thin Films with Very High Hole Conductivity.

Amorphous transparent conductors (a-TCs) are key materials for flexible and transparent electronics but still suffer from poor p-type conductivity. By developing an amorphous Cu(S,I) material system, record high hole conductivities of 103-104 S cm-1 have been achieved in p-type a-TCs. These high conductivities are comparable with commercial n-type TCs made of indium tin oxide and are 100 times greater than any previously reported p-type a-TCs. Responsible for the high hole conduction is the overlap of large p-orbitals of I- and S2- anions, which provide a hole transport pathway insensitive to structural disorder. In addition, the bandgap of amorphous Cu(S,I) can be modulated from 2.6 to 2.9 eV by increasing the iodine content. These unique properties demonstrate that the Cu(S,I) system holds great potential as a promising p-type amorphous transparent electrode material for optoelectronics.

Strong anisotropy and layer-dependent carrier mobility of two-dimensional semiconductor ZrGeTe4.

Layered ZrGeTe4 is a new type of ternary anisotropic semiconductor. The strong in-plane anisotropy may give us another degree of freedom for controlling electrical and optical properties, and designing advanced nanodevices. Using first-principles calculations, physical properties such as band structure, phonon vibration, and carrier mobility of layered ZrGeTe4 from bulk to monolayer were investigated. The bulk and few-layer ZrGeTe4 are predicted as indirect bandgap semiconductors, but the monolayer ZrGeTe4 turns out to be a direct band gap semiconductor with moderate value of 1.08 eV. Electronic structure calculations reveal that the van der Waals interaction is the main reason of causing the transition from indirect band gap to direct one. Phonon calculations demonstrate that the layered ZrGeTe4 is mechanically stable and anisotropic. In orders of magnitude, the predicted average carrier mobility of ZrGeTe4 (∼103 cm2 V-1 s-1) is between that of graphene (∼105) and MoS2 (∼102), and the anisotropy of electronic mobility is similar to that of black phosphorus, while hole mobility varies with the numbers of layers.