Mobility and Decay Dynamics of Charge Carriers in One-Dimensional Selenium van der Waals Solid

Abstract

Trigonal selenium is a semiconducting van der Waals solid that consists of helical atomic chains. We studied the mobility and decay dynamics of excess electrons and holes moving along the selenium chains. Excess charge carriers were generated by irradiation of powdered selenium with 3 MeV electron pulses. Their mobility and decay via trapping or recombination was studied by time-resolved microwave conductivity measurements as a function of temperature. The mobility of charge carriers along the Se chains is at least ca. 0.5 cm2·V–1·s–1 at room temperature. Charges decay predominantly by trapping at defects. The appreciable mobility, together with the potential for large-scale production of Se wires by liquid exfoliation, makes this material of great interest for use in nanoelectronics.

Charge Mobility and Recombination Mechanisms in Tellurium van der Waals Solid

“…In our previous work on Se, electrons and holes could be distinguished because it was known from literature that electrons are trapped faster than holes. 9,49 Such information is not available for Te and consequently we cannot distinguish electrons and holes. Hence, the charge carrier densities and related rates and mobilities are denoted as n 1 for one type of charge and n 2 for the counter charge.…”

“…The microwave conductivity studies were performed at frequencies in the range of the K a band (27–38 GHz), similar to our previous studies. 9,25 Uniform densities of excess electrons and holes were generated by irradiation with 3 MeV electron pulses from a van de Graaff accelerator, along with Bremsstrahlung irradiation, which was produced by retarding the electron pulses by a 2 mm lead (Pb) sheet. The high-energy Bremsstrahlung photons generate electron–hole pairs along their paths through the sample.…”

“…As tellurium is a heavy material, with atomic number Z = 52, density ρ Te = 6.2 g cm –3 , and M Te = 127.60 g mol –1 , it exhibits a comparatively higher stopping power ( S ( E ) = −d E /d x ) for the 3 MeV electrons, as compared to materials we studied previously. 9,25 A higher stopping power leads to lower average penetration depth (Δ x ) for the 3 MeV electrons in the sample, which leads to a nonuniform distribution of charges inside the sample. To avoid a nonuniform charge density, the sample height was reduced so that the high-energy electrons could pass through the sample, generating a close to uniform distribution.…”

Ultrafast photoconductivity and terahertz vibrational dynamics in double-helix SnIP nanowires

“…Bruggeman effective-medium theory has been used to describe the conductivity in inhomogeneous systems 19,33,35,36 , however, we were not able to obtain satisfactory fits to our experimental data using this model. A Drude-Lorentz model has been used to describe surface plasmon resonances in nanowires 22,25,33,37 or to describe hydrogen-like transitions in excitonic systems 38,39 .…”

“…Alternatively, modified forms of Drude conductivity, such as the Drude-Smith model [40][41][42] , are commonly used to describe nanomaterial conductivity when carrier localization arises from nanoscale morphology 21,28,35,36,39,[43][44][45][46][47][48][49] . The Drude-Smith model has been shown to fit photoconductivity spectra over a broad frequency range 43 , yield comparable conductivity to standard transport measurements 45 , and provide qualitative information about carrier localization 36 .…”