Meevasana Group, Suranaree University of Technology


Group members




















































Experimental Condensed Matter Physics

Synchrotron Radiation (SR) can produce very bright light at various wevelengths, usually from infrared up to X-ray. Due to this brightness and the wavelength tunability, SR can have a wide range of applications, including many research fields (e.g. physics, material science, biology, chemistry, environmental study and engineerings). Realizing much use of SR techniques, our group have much interest in exploiting SR techniques available at the Thai institute (Synchrotron Light Research Institute, SLRI) and the laboratories in abroad (e.g. ALS and SSRL) to various research topics. Our current research interests are on 1) transition-metal-oxide materials, 2) carbon-based materials, 3) physical phenomena at low temperature and 4) utilization of SR techniques for agricultural research.  The motivations and activities relating to these topics will be summarized below. For more details about our wroks, see Publications section.


1) Transition-metal-oxide materials exhibit a wide range of functional properties, such as high-temperature superconductivity, colossal magnetoresistance or multiferroicity. Spurred by the seminal discovery of Ohtomo and Hwang in 2004, attempts to exploit the wider functionality of transition-metal oxides into electronic devices have then started in order to go beyond the conventional semiconductor ones. One of the main focuses has been on two-dimensional electron gases (2DEGs) at the interface between LaAlO3 and SrTiO3. Taking part in this focus, we looked into the electronic structure of SrTiO3 (strontium titanium oxide) by using Angle-resolved photoemission spectroscopy (ARPES, a SR technique) to try understanding the origin of its unique properties. We were able to see electron interactions which were not observed before and we also found a new methodology (possibly fast and inexpensive) to create and control 2DEG on the bare SrTiO3 surface, which might be used for manufacturing all-oxide devices. Our experiments were performed at ALS (USA) and SLRI (Thailand). With TRF-CHE-SUT grant as my financial support, the SrTiO3 works were published in two high-quality journals: W. Meevasana, et al. Nature Mater. 10; 114-118 (2011) (impact factor = 29.5) and W. Meevasana, et al. New J. Phys. 12; 23004 (2010) (impact factor = 3.3). Besides the SrTiO3 works, we also studied other oxides such as copper oxide compound (published in P.D.C. King et al., Phys. Rev. Lett. 106; 127005 (2011) as a coauthor (impact factor = 7.3)) and tantalum oxide compound (manuscript in preparation.)


2) Carbon-based materials, especially graphene, recently gained much attention after Geim and Novoselov (2010 Nobel Prize Laureates in Physics) discovered many unique physical properties of the two-dimensional material graphene. With this interest, we use low energy electron microscopy (LEEM) and photoemission electron microscopy (PEEM, a SR technique) for investigating the parameters which can affect the growth of graphene layers. From the detailed investigation, we found that step/scratch on substrate surface can affect the number of graphene layers. This effect might be used as a method for patterning graphene with different layer numbers on devices; the manuscript of this work is in preparation and will be submitted to a journal in 2011. Besides the graphene study, we also applied the photoemission spectroscopy (PES, a SR technique) for studying diamondiod properties. Diamondoids are carbon-based materials with nanoscale-diamond structure; although having physical properties similar to real diamond, its low production cost of diamondoids makes their applications attractive. In our study, we found that diamondoid could be used as an efficient electron emitter which might find applications in electronics. The early work was published in Y.L. Wang, et al. Science 316; 1460 (2007) (impact factor = 29.7) (as a coauthor). The extended work, performed inclusively in Thailand, was published in W. Meevasana, et al. Appl. Surf. Sci. 256; 934 (2009) (impact factor = 1.6). The research on this topic is funded by Thailand Center of Excellence in Physics (ThEP).


3) Physical phenomena at low temperature, which can occur in many interesting forms of quantum states ranging from superconductivity, quantum Hall effect, Kondo effect, magnetic vortex, and etc., have been actively studied in many countries around the world, such as Europe, Japan, USA. Although applications at low-temperature may seem limited, there are actually many tools used in various fields (e.g. magnetic resonance imaging (MRI) for medical purpose, NMR technique as a common analysis tool) and there is much more of the common knowledge gained only from the low-temperature phenomena which can be used for a wide range of temperature/ room temperature. Despite of the scientific merit, there are only a small number of laboratories in Thailand which can perform experiments at temperature below 10 K (-263 C). Due to this lack of low-temperature equipments, our group is currently setting a small station with cryostat at SUT for studying physical properties of materials at low temperature and we also plan to utilize the SR technique together with this cooling capability. The first experiments are expected to begin in Nov. 2011 and the focus will be on electrical properties of transition-metal oxides. This research is funded by the grant from SUT and National Research Council of Thailand (NRCT).


4) Utilization of SR techniques for agricultural research is our latest research interest to apply advanced physics tools for the research topic which has a high impact to the Thai society. The focus is on using x-ray absorption spectroscopy (XAS, a SR technique) for analysis and development of phosphate fertilizer extracted from agricultural and livestock waste. As the phosphate rock (raw material for phosphate fertilizer) is limited resource and its price keeps rising, an alternative source should be considered. Processing wastes to get high-quality phosphate fertilizers (comparing to chemical fertilizer) is proven possible at relatively low price from the 2009 pilot project in Europe. However, as the wastes can be in different forms, we still need an advanced tool to accurately analyze the quality (i.e. forms of phosphate compounds) of the processed fertilizers. The XAS technique, which we use for our analysis to get the high-quality phosphate fertilizer extracted from agricultural and livestock waste, appears to be one of the few best tools for such purpose. This project is initiated this year and the early results already show that we can distinguish various forms of phosphate compounds in organic and chemical fertilizers; more experiments are currently under preparation. The funding of this research topic partly comes from ThEP.