Chemistry and Biochemistry
STM/STS of gate oxides on compound semiconductors and adsorbates on organic semiconductor
As semiconductor devices decrease in size to atomic dimensions, an atomic level knowledge of the interfaces in semiconductors device is required. We combine the vapor deposition of oxides and organic semiconductors with scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and density functional theory (DFT) computations to develop a fundamental understanding of the chemistry and physics of semiconductor interfaces.
oAtomic Structure of Interfaces of Gate Oxides on Semiconductors: As semiconductor gate lengths shrink below 150 nm, the gate oxides must become thinner and have a higher dielectric constant. Our group is studying deposition processes and bonding structures that result in electrically passive interfaces between high-k oxides and many semiconductors surfaces. By studying the adsorption of Ga2O, In2O, SiO, O, and O2 on GaAs(001) STM, STS, and DFT calculations, we have been able to obtain an atomistic understanding of Fermi level pinning and unpinning at the GaAs(001)/oxide interface. Current aspects of this project include (a) oxides interfaces on InAs which has over 20x the electron speed of silicon, (b) oxide interfaces on AlGaAs which is used in InP devices, (c) oxide interfaces on Ge which has over 4x the hole speed of silicon, and (d) cross sectional STM of oxide-semiconductor interfaces.
oChemical Sensing with Metal Phthalocyanines: Metal phthalocynaines (MPcs) can be used as the carrier layer in transistors (ChemFETs) to fabricate a gas sensor with very high sensitivity (ppb) because MPcs change from insulating to semiconducting upon gas absorption. We are studying the formation of the MPcs films and gas adsorption on MPcs with STM. In addition, we are using vacuum deposition to form gas sensors with MPcs.
Over the years, I have directed a program at the cancer center entitled ET CURE to support under-represented minority (URM) undergraduate, graduate students, postdoctoral associates, and PhDs who are using new technologies, primarily nanotechnology, in cancer research. As far as I know, during this time, I have enabled more funding to be obtained for URM students/postdocs than most other UCSD faculty members in science and engineering.
oOutside the cancer center, I used the San Diego Fellowships I obtained as matches on my grants to support women students who are considered under-represented in physical science and most engineering disciplines (ie. all but chemical engineering and bioengineering).:
oMy best estimate is the average funding I have enabled for URM students and postdocs is about $500,000/yr (direct + indirect). The NCI has pointed out on numerous occasions that due to our aggressive effort in URM recruitment, UCSD alone represents over half the funding for ET CURE participants at the graduate and postdoctoral level.
oI have used the relationships I have developed at the cancer center to advance both URM recruitment and education and develop an R25T the training grant proposal for nanotechnology in cancer research which will support graduate students and postdocs. The excellence of our program has been noted in the reviews of the R25T training grant. Reviewers noted that UCSD has an outstanding reputation in minority recruitment for nanotechnology in cancer: "The Institution (UCSD Cancer Center) is also known for its success in recruiting and supporting underrepresented minorities."
oI hope to continue to aggressively pursue more funding for our URM graduate students and continue to place the students in various research groups.