STM detection of single electron and nuclear spins
ESRSTM (electron spin resonance scanning tunneling microscopy )is a technique capable of detecting single spins by recording the power spectral density at the Larmor frequency - in the tunneling current. Description of previous results will be provided. Recently a Si(111)7 × 7 surface exposed to 0.1 L of O_2 and the carbonized Si(111) surface are investigated by ESR-STM using frequency sweeps and magnetic field sweeps. Only after oxidizing the clean Si(111)7 × 7 or by using the carbonized Si(111), spatially averaged ESR-STM spectra exhibit several peaks and dips around the frequencies corresponding to g = 2. The energy difference between these features is close to the known hyperfine splitting of A ≅ 9 MHz for vacancies in SiC interacting with next-nearest neighbor ^29 Si. The final proof that the hyperfine spectrum is indeed observed, is the observation of the nuclear Zeeman transition of a single nuclear spin that were observed by an ENDOR type experiment. The results of this experiment reveals the gyromagnetic ratio of 29^Si nuclei. ESRSTM was observed also on Cu atoms. The ENDOR experiment will be carried out to detect the gyromagnetic ratios of the two types Cu nuclei. These results were performed in frequency domain. In this mode the technique is time consuming as the different frequency components are detected one after the other. In time domain, the acquisition is orders of magnitude faster. Results on adsorbed Tempo molecules will be presented. These results display the whole spectrum from 0-0.75GHz. The results reveal the expected Larmor frequency components of Tempo (f1) and additional higher frequency components that are interpreted as tip spin centers (f2). In addition strong peaks appear at a frequency (f1-f2)/2 which may point to a possible mechanism of interference between electrons that are propagating through tip and sample spin centers, respectively.