Microspot photoemission spectrometer based on FS-VUV radiation

The lateral resolution of our laser-based microspot photoemission spectrometer [Surf. Sci. 507–510 (2002) 434] has been improved to 0.3 μm by focusing VUV light of 140 nm wavelength (8.9 eV photon energy). The VUV light is generated by frequency tripling a second-harmonic output of a regeneratively amplified titanium:sapphire laser of 250 kHz repetition rate, and is focused on a sample surface by a Schwarzschild objective of 0.29 NA. Time-of-flight (TOF) photoelectron spectra of energy resolution better than 40 meV are accumulated for 0.4 s during scanning the sample position by 0.1 μm/step. Measurement on a Ta-striped Si sample revealed that the lateral resolution is 0.3 μm, which is very close to the diffraction-limited spot diameter. The present microspectrometer is characterized with the simultaneous realization of the diffraction-limited lateral resolution and the high-energy resolution, which is close to the Fourier transform of the pulse width of the laser light (100 fs).