Yashar Azizian-Kalandaragh

This study examines the frequency- and voltage-dependent electrical parameters, interface trap densities ([ ]) and relaxation times ([ ]) in Au/PVA:(CoFe ₂ O ₄ -rGO)/n-Si structures using three complementary admittance methods. CoFe ₂ O ₄ nanoparticles, synthesized hydrothermally, were incorporated with reduced graphene oxide (rGO) into polyvinyl alcohol (PVA) matrices and spin-coated onto n-Si substrates to form interfacial layers. Capacitance–voltage (C–V) and conductance–voltage (G/[ ]–V) measurements spanned [ ]2.0–[ ]3.0[ ]V across 0.3[ ]kHz–3[ ]MHz. Pronounced frequency dispersion was observed: forward-bias capacitance at [ ]3.0[ ]V fell from [ ]9[ ]nF (0.3[ ]kHz) to [ ]2.5[ ]nF (3[ ]MHz), while the normalized conductance peaked near 0.8–1.0[ ]V at all frequencies, with trap saturation above [ ]0.75[ ]V. Hill–Coleman analysis revealed [ ] values that decline quasi-exponentially from [ ] [ ]eV[ ] [ ]cm[ ] at low frequencies to [ ] [ ]eV[ ] [ ]cm[ ] at high frequencies. Parallel-conductance extraction revealed [ ] spanning three orders of magnitude, from [ ]120[ ] [ ]s at 0.20[ ]V to [ ]0.08[ ] [ ]s at 1.60[ ]V, with the normalized conductance saturating above [ ]0.75[ ]V, consistent with strong field-induced acceleration of trap dynamics and near-complete filling of accessible trap levels under moderate forward bias. This behavior arises because the AC period shortens relative to [ ]: once the period falls below the trap response time, slower states cease contributing to the measured admittance. The apparent donor concentration decreased from [ ] [ ]cm[ ] to [ ] [ ]cm[ ] over the same frequency range, while the depletion width expanded from [ ]6.6[ ][ ]m to [ ]39.9[ ][ ]m, and the peak electric field diminished from [ ] [ ]V/cm to [ ] [ ]V/cm over the same frequency. Unlike conventional low-dielectric interlayers that cannot fully suppress interface states or reduce series resistance, the high-dielectric PVA:(CoFe ₂ O ₄ -rGO) nanocomposite studied here offers a broader operating window by neutralizing a substantial fraction of [ ] while regulating charge transport mechanisms. To our knowledge, this is the first frequency-resolved, multi-method mapping of [ ] and [ ] distributions in such a system, offering practical guidance for engineering nanocomposite interlayers with tailored trap spectra.

We present a maskless method for fabricating transmission-type diffractive optical elements (DOEs) using aerosol jet printing (AJP). To our knowledge, this work represents a systematic proof-of-concept demonstration of AJP for DOE fabrication. Five distinct geometries were directly printed from CAD designs without masks or cleanroom facilities. Structural characterization using atomic force microscopy (AFM), optical microscopy, profilometry, and XRD confirmed high pattern fidelity. Optical performance under coherent laser illumination showed good qualitative agreement with FFT-based simulations. This approach provides a rapid, cost-effective (<$5persample), and environmentally friendly prototyping method that complements conventional lithography for passive diffractive components.