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I have several areas of research which focus mainly on the basic materials processes such as nucleation and growth processes in metal/semiconductor systems. We work on problems which have a direct connection to microelectronics applications. Some examples include the following:

Silicides for Silicon Source/Drain contacts

Phys. Rev. B 49,13501-13511 (1994), Appl. Phys. Lett. 65, 561-563 (1994), J. Appl. Phys. 77, 4384-4388(1995), "Symposium for Microelectronic Silicides," MRS (1996).

Ohmic contacts

GaN [APL 64, pg.1003, 1994]; GaAs [APL. 51, pg. 326, 1987]

Diffusion Barriers

US Patent #5,023,201 (1991), US Patent #5,138,432 (1992), JAP, 79, 2446-2457 (1996), APL, 60 3179 (1996), Patent Filed #96-096, (1996).The second area of research involves the development of a new tool for materials studies:

Nanocalorimetry

Our group has invented a new Thin Film Scanning Calorimetry TDSC device. TDSC is the most sensitive scanning calorimetry device yet reported being 100-1000 times more sensitive than conventional systems. Our objective is to use the technique in two new areas: dynamic energy measurements at surfaces and sensor technology. The first steps toward these objectives have been extremely successful.

Scanning Nano-Calorimetry

Differential Scanning Calorimetry (DSC) is a technique to measure heat exchange during chemical reactions or phase transformations. We have taken the old concept of scanning calorimetry and transformed it into a new powerful characterization/sensor device using micro-machining techniques. This has expanded DSC from traditional 3-D bulk systems to 2-D surface systems. Our TDSC is built upon the idea of the micro-heater, a thin strip of metal which we heat at extremely fast rates ~ 1,000,000 C/s by pulsing large currents through it. The TDSC is the most sensitive calorimetry system yet reported (0.2 nJ), capable of measuring the energy equivalent to melting 0.1 monolayer of atoms.

Size-Dependent Melting Point

We demonstrated the power of TDSC in our melting point study of Sn nanostructures. We are the first to show that both the melting point Tm and the heat of fusion Hm decrease when the physical size of the Sn structures decreases (<20nm). When 1è of Sn is deposited onto an inert substrate, the Sn atoms self-assemble into small islands (nanostructures) consisting of ª 1000 atoms. We found that these islands melt at Tm = 110C, far below the bulk value of 232C. At this stage, our TDSC technique is posed to answer key questions about the basic nature of the melting process, especially regarding surface pre-melting. Melting point depression of small particles has two strong implications for microelectronics technology: (i) control of crystallographic texture for metals during the early stages of film growth during island formation, and (ii) the stability/reliability of aluminum interconnect lines which will have dimensions of only 70 nm by the year 2002. Will these lines be solid or liquid at these dimensions?