Saime Sebnem Cetin

Plasmon-Enhanced Photocatalysis on Anisotropic Gold Nanorod Arrays

The field of photocatalysis is an active area owing to the possible contributions to solve some challenging problems such as sustainable energy production, environmental pollution control, and even global warming. Unfortunately, traditional photocatalysts, especially semiconductors, suffer from inherent deficiencies, which include high activation barriers, the low mobility of charge carriers, and poor long‐term stabilities. Herein, we demonstrate a plasmonic photocatalyst based on unidirectional gold nanorod arrays fabricated by using the oblique‐angle deposition (OAD) technique. The fabricated gold nanorod arrays exhibit a remarkable plasmonic anisotropy, which depends on the direction of the incoming light. By employing these arrays as a plasmonic catalyst, a clear improvement and control in the catalytic reduction of o‐nitroaniline to 1,2‐benzenediamine, depending on the directionalities and anisotropic plasmonic properties of the gold nanorods, was obtained. These results suggest that such unique characteristics of directional gold nanorod arrays could greatly impact several technological areas, not only in plasmon‐enhanced photocatalysis but in biosensing and optofluidic applications.

New method and treatment technique applied to interband transition in GaAs1−xPx ternary alloys

In this paper we presented a new method (Eigen-Coordinates (ECs)) that can be used for calculations of the critical points (CPs) energy of the interband-transition edges of the heterostructures. This new method is more accurate and complete in comparison with conventional ones and has a wide range of application for the calculation of the fitting parameters related to nontrivial functions that initially have nonlinear fitting parameters that are difficult to evaluate. The new method was applied to determine the CPs energies from the dielectric functions of the MBE grown GaAs1−xPx ternary alloys obtained using spectroscopic ellipsometry (SE) measurements at room temperature in the 0.5-5 eV photon energy region. The obtained results are in good agreement with the results of the other methods.

Structural, optical and electrical characterization of dilute nitride GaP1−x−yAsyNx structures grown on Si and GaP substrates

The structural, optical and electrical properties of dilute nitride p–n junction GaP1−x−yAsyNx structures grown on n-type GaP (100) and n-type Si (100) misoriented by 4° towards the [110] direction substrates were studied. These properties of the samples, which were grown by using molecular beam epitaxy (MBE) technique, were investigated by using high-resolution X-Ray diffraction (HRXRD), energy dispersive X-Ray (EDX), room temperature photoluminescence (PL) and current–voltage (I–V) measurements. Both alloy composition values (x, y) and crystal structure parameters were determined from HRXRD measurements while the band gap energies were obtained from PL measurements. Composition values were also determined by using EDX measurements and compared with HRXRD results. The better crystal quality was found for the sample grown on GaP substrate from both the HRXRD and PL results. In addition, the theoretical band gap energies calculated from the band anticrossing (BAC) model and experimental band gap energies determined from the PL measurements were compared and found to be in good agreement with each other. The p–n junction GaP1−x−yAsyNx/GaP (Si) diode devices were fabricated to investigate their electrical properties. The I–V characteristics of diodes were analyzed at room temperature and the diode formed on GaP substrate exhibited better results compared to other diode.

Optical, Electrical, and Crystal Properties of TiO 2 Thin Films Grown by Atomic Layer Deposition on Silicon and Glass Substrates

TiO2 thin films have been deposited on glass and Si(100) by atomic layer deposition (ALD) technique using tetrakis(diethylamido)titanium(IV) and water vapor as reactants. Thorough investigation of the properties of the TiO2/glass and TiO2/Si thin films was carried out, varying the deposition temperature in the range from 100°C to 250°C while keeping the number of reaction cycles fixed at 1000. Physical and material property analyses were performed to investigate optical and electrical properties, composition, structure, and morphology. TiO2 films grown by ALD may represent promising materials for future applications in optoelectronic devices.