Scanning Probe Microscopies

Title: Scanning probe microscopies (Marshall Stoneham, Sasha Shluger, Lev Kantorovich, Aleks Livshics)

Context: Scanning Probe Microscopy has normally been used for imaging. But it has several other roles: as a mimic of asperities for surfaces in contact, and as a probe (laboratory on a tip) which can perturb existing defects in appropriate ways, including ways to make imaging better. We were the first to point out that an STM tip will displace atoms when one is merely trying to image adsorbed species (i.e., NOT trying to move them) and that the STM tip can significantly affect surface vibrations.

Current activities: Our main current interests are twofold:

(1) STM as a means to study non-radiative transitions (EPSRC funded). Since the characteristic timescale for non-radiative transitions is 10-9 sec and since that of STM is, say, 10-4 sec or more, this may seem a non-starter. But one can choose systems which do not normally luminesce, and push them into radiative recovery using the STM as a probe. This is our aim through state-of-the-art modelling (and through collaborations with our friends who do experiments)

(2) AFM as a means to understand tribocharging (EPSRC ROPA funded), and to link AFM to macroscopic phenomena by mesoscopic modelling. Our earlier work has shown how one can model friction, wear and charge transfer on the atomic scale. Our present work has to go further, including electron tunnelling and a variety of non-equilibrium phenomena.

People involved (including external collaborators)

John Pethica and Adrian Sutton (Oxford), Mark Welland (Cambridge), Carl Sofield (AEA Technology), Marta Ramos (University of the Minho, Portugal), Richard Williams (Wake Forest),

Recent (or simply relevant) papers

279. Effects of the STM Tip on Atomic Positions: an Explanation for the nonobservation of adsorbed molecules?
M M D Ramos, A M Stoneham, A P Sutton and J B Pethica, 1990, J Phys Cond Mat 2 5913-5917.

301. Effects of the STM Tip on Adsorbate Images.
M M D Ramos, A P Sutton and A M Stoneham 1991 J Phys Cond Mat 1 (SuppA) S127-S131

316. How do they stick together? The statics and dynamics of interfaces.
A M Stoneham, M M D Ramos and A P Sutton 1993 Phil Mag A67 797-811.

323. Effect of the STM tip on Si (100) Reconstructed Surface.
M M D Ramos, A M Stoneham and A P Sutton 1993 J Phys Cond Matt 5 2849-2858.

Cross-links Studies of surface spectroscopies, like MIES (collaboration with Volker Kempter, Clausthal). Studies of solid-state gas sensors (David E Williams, UCL Chemistry)