Email: email@example.comTelephone: 0207 882 6572Room Number: G. O. Jones Building, Room 211
1st Supervisor: Alan Drew
2nd Supervisor: David Dunstan
Project Title: Photo-μSR spectroscopy in semiconductors.
Muon spin relaxation, rotation and resonance spectroscopy called μSR technique has proved to be an effectively probe of magnetic field. This technique is at a microscopic level to have an insight into its magnetic and electronic properties. Such as superconduc- tors, semiconductors and various class of magnetic materials and organic materials. The tremendous advantage as a magnetic resonance technique is that the 100% spin-polarised muon implantation and thermalisation occur so rapidly which makes the depolarisation is insignificant.
One of the direction is to measure the excess carrier lifetime in silicon. The experimentally measured recombination rate is composed of bulk and surface recombination. The surface recombination should be significantly faster than the bulk recombination and the bulk term can be divided into three components:1/τbulk=1/τSRH+1/τrad+1/τAuger. However, as we use the Si wafers which are grown by the float zone scheme is known to have a very low defects in the bulk crystal structure, hence it minimises the SRH(Shockley-Read-Hall) term in Eq.1 and the surface are polished and coated with a thin oxide layer to passivate the surface defects, which minimises the effect of the surface recombination. If we want to measure the photocarrier lifetime in low temperature regime we must know whether the Auger recombination have the same dependence on the excess carrier density as the room temperature or not. Muon can give the answer by the photo-MuSR technique, which is a sensitive probe of the photoinduced carriers in semiconductors.
The other project is to use Photo-μSR to detect exciton dynamics in organic semiconductors. This is a laser-excited muon pump-probe spin spectroscopy. Several experiments has been done on organic semiconductors such as TIPS-pentacene. Time dependent light-induced changes on muonium avoided level crossing resonance has been observed which shows that the electrophilic photochemical reactivity of a specific carbon atom is modified as a result of a localization of the excitonic wavefunction. Now we are researching on how sinlet and triplet excitons affect Mu in solid state TIPS (thin film).
Examples of research funding:
China Scholarship Council
K.Yokoyama, J.S.Lord, J.Miao et al. PRL 119, 226601 (2017) A new method for measuring excess carrier lifetime in bulk silicon: Photoexcited muon spin spectroscopy.
S Han, et al., Room temperature spin correlation in an f-electron single ion molecular magnet, submitted to Nature Communications. (2018)