Abstract
In this paper, the authors present the characterization experiments of a 20 fs vacuum ultraviolet beam from a high harmonic generation source. The beam hits a silicon sample and passes a triple reflection gold polarizer located inside an ultrahigh vacuum chamber. The polarizer’s Malus curve was obtained; the total acquisition time for each point of the curve was 30 s. This aims to be the first vacuum ultraviolet time-resolved user station dedicated to ellipsometry. The high harmonic beam is generated by a 12 mJ, 1 kHz, 20 fs, in-house-developed laser and detected by a back-illuminated charge-coupled device.
Highlights
Vacuum ultraviolet (VUV) ellipsometry is a powerful complementary technique to VUV reflectance as it provides better capabilities to study thin film and layered materials due to the degree of freedom introduced by the light phase
The possibility of building cost-effective high harmonic generation (HHG) sources drives the recent interest in transient VUV reflectance experiments using laser driven HHG secondary sources
HHG was done in neon or argon gas and was analyzed before being sent to the ELIps instrument by the VUV spectrometer of the HHG beamline consisting of a toroidal mirror, a motorized slit of variable width, a reflection grating, and a back-illuminated charge-coupled device (CCD)
Summary
Vacuum ultraviolet (VUV) ellipsometry is a powerful complementary technique to VUV reflectance as it provides better capabilities to study thin film and layered materials due to the degree of freedom introduced by the light phase. VUV ellipsometry allows the possibility of studying large bandgap semiconductors and allows the study of transitions from shallow core levels. The interpretation of core level to conduction band transitions has been shown to be easier than the interpretation of valence to conduction band excitations.. Commercial VUV ellipsometers achieving up to 8.86 eV (140 nm) are currently available. The only ellipsometer available is the one at the Metrology Light Source of the Physikalisch-Technische Bundesanstalt (PTB) in Berlin, which uses synchrotron light and has a documented VUV operational energy range extending up to 40 eV. The possibility of building cost-effective high harmonic generation (HHG) sources drives the recent interest in transient VUV reflectance experiments using laser driven HHG secondary sources. Among recent publications is a study on time-resolved VUV absorption on germanium.. Among recent publications is a study on time-resolved VUV absorption on germanium. Important work has been done on probing ultrafast element-specific magnetization dynamics targeting, e.g., M-absorption edges of Fe (54 eV) and Ni (67 eV).
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