Browsing by Author "Aydemir, Umut"

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Open Access
ANN-based estimation of MEMS diaphragm response: An application for three leaf clover diaphragm based Fabry-Perot interferometer
(Elsevier BV, 2022-06-23) Yigit, E.; Hayber, Ş. E.; Aydemir, Umut
In this study, an artificial neural network (ANN) based model is developed for MEMS diaphragm analysis, which does not require difficult and time-consuming FEM processes. ANN-based estimator is generated for static pressure response (d) and dynamic pressure response (f) analysis of TLC (three leaf clover) diaphragms for Fabry-Perot interferometers as an example. TLC is one of the unsealed MEMS design diaphragms formed by three leaves of equal angles. The diaphragms used to train ANNs are designed with SOLIDWORKS and analyzed with ANSYS. A total of 1680 TLC diaphragms are simulated with eight diaphragm parameters (3 for SiO2 material, 4 for geometry, and 1 for pressure) to create a data pool for ANN’s training, validation, and testing processes. 80% of the data is used for training, 15% for validation, and the remaining for testing. Only four geometric parameters are used as input in the ANN estimator, and the material parameters are added to the model with an analytical multiplier. Thus, network models that estimate d and f values for all kinds of diaphragm materials are proposed, with a material-independently trained ANN structure. The performance of the ANN model is compared with the empirical equation suggested in the literature, and its superiority is demonstrated. In addition, the d and f parameters of TLC diaphragms designed with five different materials (Si, In2Se3, Ag, EPDM, Graphene) are estimated to be very close to the real ones. By using the proposed method, analyses of TLC diaphragms are quickly performed without the need for time-consuming and costly design and analysis programs.
Open Access
Design and simulation of a novel fungus-shaped center embossed diaphragm for fiber optic pressure sensors
(Elsevier, 2020-12-19) Hayber, Ş. E.; Aydemir, Umut
A novel structure with a fungus-shaped center embossed diaphragm (FCED) geometry has been proposed to modify in diaphragm-based Fabry-Perot fiber optic pressure sensors (FP-FOPS). The proposed FCED geometry was obtained by adding a pillar between the mesa and diaphragm. Before the simulation analysis of FCED, we derived mathematical equations of attenuation factor widening the acceptance radius. The attenuation factor is defined to understand sensor loss, which is neglected in the literature. With this derived formula, the light reflected from the deflected diaphragm and the light unguided in the fiber was detected. Since the deformation angle is zeroized in the FCED structures, the sensor loss due to the attenuation factor is eliminated. All the incident light being re-guided in the fiber. With FCED design’s help, the decreasing sensitivity in the center embossed diaphragms (CED) has been prevented. Moreover, the deviation of the frequency response of FCED remains lower than 1% compared with the results of conventional diaphragms. As a result, it produces a more stable sensor, and the FCED structure is less affected by manufacturing errors. The researchers can benefit from the use of our presented results when designing and producing new diaphragm-based FP-FOPS.
Open Access
Enhanced photoresponse of PVP:GaSe nanocomposite thin film based photodetectors
(Institute of Physics Publishing Ltd., 2022-02-21) Demirtaş, T.; Odacı, C.; Aydemir, Umut
Two-dimensional materials have become the focus of attention of researchers in recent years. The demand for two-dimensional materials is increasing day by day, especially with the inadequacy of graphene in optical applications. In this context, the optical and electrical characteristics of the PVP:GaSe thin film nanocomposites were investigated. The surface morphologies of the samples were characterized by SEM, the thin film thicknesses and refractive index parameters were measured by the Ellipsometer method, the structural characteristics were obtained by XRD, and Raman and PL spectroscopy was used to determine the optical characteristics. Critical parameters of Au/PVP:GaSe/n-Si photodetector were calculated under various illumination intensities. It is observed that photodetector with PVP:%5GaSe thin film has the best performance results. According to the experimental results, its responsivity, external quantum efficiency, and detectivity values are 0.485 A W−1, %86, and 1.14 × 107 cm Hz1/2 W−1 respectively.
Open Access
Fabrication and characterization of printed phototransistors based on monochalcogenide inks
(American Chemical Society, 2023-04-04) Odacı, C.; Muehleisen, W.; Aydemir, Umut; Roshanghias, A.
Two-dimensional (2D) layered semiconductors of Group-III monochalcogenides have gained increasing attention in photonics and electronics. The fabrication of large-scale, inexpensive inks which can be used in printed electronics applications is facilitated by the solution processing of 2D materials. In this study, gallium sulfide (GaS)-, gallium selenide (GaSe)-, and gallium telluride (GaTe)-loaded inks were synthesized and implemented to fabricate phototransistors on SiO2\Si substrates. To explore the printed device performances, several color illuminations were applied to the printed phototransistor, and the mobility, photoresponsivity, and external quantum efficiency parameters were compared. Under red-light illumination, the mobility of a GaTe nanoparticle-based phototransistor reached 7.456 cm2 V-1 s-1. The responsivity of the GaTe-based phototransistor was found to be the highest, with the value of 9.52 A W-1 under green light illumination. However, GaSe-based phototransistors gave the highest EQE value of 2482 (%) under blue light illumination with the mobility of 7.04 cm2 V-1 s-1. This study demonstrates that printable Group-III monochalcogenide inks can be synthesized with desired properties for use in printed electronic applications.