Photoconductivite et photoemission de diamant(s) sous irradiation XUV femtoseconde

TL;DR

This study investigates the photoconductivity and photoemission in diamonds under femtosecond XUV irradiation, revealing complex carrier dynamics influenced by plasmon relaxation and electron interactions, with theoretical insights into carrier lifetimes.

Contribution

It provides new experimental data on diamond photoconductivity with femtosecond XUV pulses and introduces ab-initio calculations of carrier lifetimes considering electron-electron interactions.

Findings

Photoconductivity increases then decreases with harmonic order.

Strong plasmon relaxation effects influence carrier multiplication.

Carrier lifetime behavior aligns with Fermi-liquid model near bandgap.

Abstract

We report a study of the photoconductivity (PC) induced in different types of diamonds (type IIa single crystals and CVD) by femtosecond XUV pulses (high order harmonics - up to 19th - of a titanium doped laser). We also reprot UPS spectras obtained with harmonics 13 to 29. Depending on the harmonic's order, the PC signal first increases (orders 9 to 13) and then decreases. If the increase is easily interpreted as resulting from a carrier multiplication process, the further decrease has not yet received an explanation. The UPS measurements also suggest a strong effect of the plasmon relaxation on the carrier multiplication process. Finally, we performed a preliminary GW ab-initio calculation of the carriers lifetime, acounting for electron-electron interactions. In the near-bandgap region, it behaves approximatively according to the Fermi-liquid model, from which it strongly departs at higher energies, which is attributed to band-structure effects and to plasmon excitations.