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Advanced Functional Materials Laboratory

The primary mission of the Advanced Functional Materials Laboratory Research Service Center (RSC) is to provide user facilities for epitaxial growth of a broad range of materials for projects in the sciences and engineering. The facilities are available to all Texas State Faculty and to external users who have established a relationship with Texas State University.

New MOCVD Capabilities

https://star.txstate.edu/node/2123

MOCVD

Molecular Beam Epitaxy

MBE Diagram

Narrow Gap Semiconductors

Narrow Gap Semiconductors

Used for the growth of Hg-based device structures for infrared imaging applications. II-VI based compound semiconductors also are being considered for a new generation of high-efficiency photovoltaic solar cells and thermoelectric devices. Infrared focal plane arrays, and the “night vision” cameras they enable, are the “eyes” that allow firefighters to see through smoke, pilots to avoid obscured visibility accidents, and soldiers to “own the night.”

IV-VI Compound Semiconductors

IV-VI Compound Semiconductors

Used for the growth of Pb and Sn-based device structures for infrared imaging and thermoelectric applications. Similar to II-VI based infrared focal plane arrays, IV-VI compound semiconductors may be the viable route to high-performance yet defect tolerant infrared imaging systems that enable “night vision” for security and military applications while opening vistas for medical or chemical sensing applications. In addition, these materials are useful for creating advanced structures for thermoelectric energy harvesting of waste heat, particularly when combined with new approaches relying on nanostructuring.

Functional Oxides

Functional Oxides

Growth of magnetic-based and other complex oxides for spintronics, sensor applications, and polarization electronics. Sources include Si, Ge, Mg, Fe, Mn, Y, Co, Zn, as well as oxygen and nitrogen. A plasma source can be used to generate neutral atomic gaseous fluxes. The system also includes electron-beam capability for deposition of various low-vapor-pressure metals for gate electrodes. An example would be to integrate complex oxides with semiconducting material to form new classes of devices with unusual properties.

Nanoscale Chemical Analysis

Nanoscale Chemical Analysis

This chamber has the capability for X-ray photoelectron spectroscopy (XPS) to determine the chemical bonding of thin films, study the evolution of interfaces and surfaces during heteroepitaxial growth, and probe the conduction band. Ultraviolet photoelectron spectroscopy (UPS) is used to probe the valence band structure of thin films and, in combination with XPS, can provide information of the complete band structure of such films. Low-energy electron diffraction (LEED) is used to determine the surface structure of crystalline surfaces. The in-situ capability of this chamber allows for the complete understanding of the growth of thin films by interrupting the deposition at various stages and probing the surface chemistry without exposure to atmosphere.

Crystalline Oxides on Semiconductors

Crystalline Oxides on Semiconductors

Growth of crystalline multifunctional oxides on oxide and semiconductor substrates as well as Si and Si/Ge heterostructures. Oxides include members of the perovskites family (SrTiO3, LaAlO3, BaTiO3), HfO and ZrO. Crystalline oxides on large-area silicon are
used as virtual substrates for the integration of other multifunctional oxides on semiconductors, allowing a common platform for integration of multiple semiconductors and devices on the same “chip.” Hf and Zr oxides are used in the development of future gate dielectric on Si CMOS to address the replacement of conventional SiO2. Electron-beam deposition of metals are studied to develop metal gates with suitable work function for both p- and n-channel devices.

Scanning Probe Microscope

Scanning Probe Microscope

Scanning probe microscopy is used to image individual atoms on a crystal surface to determine the real space position. Scanning tunneling spectroscopy also can be used to determine the density of states across the bandgap of the material and identify types of atoms. This system also is capable of atomic force microscopy to determine the surface morphology of the grown films useful in the optimizing of deposition parameters.

Compound Semiconductor As Based

Compound Semi Conductor As Based

Dedicated to growth of compound semiconductors for high-speed electronics and optoelectronic device applications. Sources include Ga, Al, In, Si, Be and As in effusion cells. RHEED is used for growth rate and composition determination and for monitoring the crystal structure during deposition. Examples of device structures include PHEMT, LEDs, lasers, optical modulators, and high-efficiency multijunction photovoltaic solar cells. A current project is the development of high-mobility channel material required for the next generation of microprocessors and memory.

High-K Dialectrics

High-k Dielectrics

Used for the development of gate dielectrics on compound semiconductors in the quest for a III-V MOSFET device. A suitable oxide is needed as a gate dielectric on compound semiconductor as the silicon industry searches for replacing the channel in CMOS with high-mobility III-V semiconductors. Examples of oxides include Ga2O3, GdGaO3, LaAlO3, GdScO3, LaLuO3 deposition using a combination of high-temperature effusion sources and electron-beam deposition. RHEED is used for determining the crystal structure of the semiconductor surfaces and for growth monitoring.

Compound Semiconductor Sb Based

Compound Semiconductor Sb-Based

Dedicated to the growth of low bandgap As-and Sb-based compound semiconductors for high speed electronics and optoelectronics devices operating in the far infrared region of the electromagnetic spectrum. These material systems are used for long wavelength detectors relevant for defense applications in addition to being used for high efficiency solar cells. Because of their high mobilities, narrow gap semiconductors are being considered for the next generation electronic devices.