Yazar "Mutale, Alex" seçeneğine göre listele

Listeleniyor 1 - 6 / 6
  • Küçük Resim
    Öğe
    The deep investigation of annealing temperature and gamma irradiation on Al2O3/Yb2O3/Al2O3/n-Si (100) MOS-like structure
    (Springer, 2023) Mutale, Alex; Zulu, Mailes Chimwemwe C.; Yılmaz, Ercan
    In this paper, we report the fabrication of Al/Al2O3/Yb2O3/Al2O3/n-Si (100) charge trapping memory device by RF magnetron sputtering technique. The structural and electrical properties of high-dielectric (k) materials at various annealing temperature have been systematically investigated. XRD analysis confirm that the thin fims were amorphous after annealing temperature above 200 degrees C. AFM shows that the root mean squared value increased with an increase in the annealing temperature. Electrical performance tests showed that annealing at lower temperature can lead to an improvement of electrical properties as shown by an increase in the memory window (Delta V-fb) and the capacitance value in the accumulation region. The Cs-137 gamma irradiation response on the device has also been studied at different doses of 4 Gy to 128 Gy with dose rate 491 Gy/h. The C-V curves slightly shifted towards the negative voltage side due to the generation of net positive oxide trapped charges(Delta N-ot) during radiation.
  • Küçük Resim
    Öğe
    Determination of frequency and voltage dependence of electrical properties of Al/(Er2O3/SiO2/n-Si)/Al MOS capacitor
    (Springer, 2020) Aktağ, Aliekber; Mutale, Alex; Yılmaz, Ercan
    In this study, we investigated the effects of applied voltage and frequencies on the electrical properties of Al/(Er2O3(150 nm)/SiO2(20 nm)/n-Si)/Al MOS capacitor. The e-beam deposited Er2O3/SiO2 films were annealed at 650 degrees C in N-2 ambient and the crystal and phase identification of the films were confirmed by X-ray diffractometry. The capacitance-voltage (C-V) and the conductance-voltage (G/omega-V) measurements of the MOS capacitor were carried out for voltage frequencies from 50 kHz to 1 MHz at several steps. The parameters of doping concentration, diffusion potential, built-in potential, barrier height, Fermi energy level, the image force barrier lowering and the depletion layer width were calculated by C-V and G/omega-V data. While the depletion layer width decreased with increasing frequencies, the diffusion potential and the barrier height increased a little with small frequencies (200 kHz <= f) first, then decreased insignificantly. We also studied the frequency effects on the series resistance (R-s) and the interface state density (D-it) through the C-V and G/omega-V curves, and found noticeable decreases in R-s and D-it values with increasing frequency. The measured and calculated results reveal that both R-s and D-it frequency dependence have significant impacts on Er2O3/SiO2/n-Si MOS capacitor properties. These effects are basically because of the interfacial charge behavior of thin SiO2 layer contained in between n-Si and Er2O3.
  • Küçük Resim
    Öğe
    Effect of annealing temperature on the electrical characteristics of Al/Er2O3/n-Si/Al MOS capacitors
    (Elsevier, 2021) Mutale, Alex; Deevi, Seetharama C.; Yılmaz, Ercan
    In this work, Er2O3 films deposited by electron beam (E-beam) evaporation technique were annealed at 450 °C, 550 °C, and 650 °C in N2 atmosphere for 30 min. We then compared the electrical properties, the frequency dependency of the density of interface states, and series resistance of as-deposited and annealed Al/Er2O3/n-Si/Al MOS capacitors. The grain size measurements carried out by X-ray diffractometer (XRD) and the root mean square (RMS) surface roughness values obtained by atomic force microscopy (AFM) increased with an increase of annealing temperature. The C-V and G/?-V measurements were carried out at a frequency of 1 MHz for as-deposited and annealed MOS capacitors. The capacitance in the accumulation region decreased with an increase in annealing temperature, and the capacitor film annealed at 450 °C had the highest capacitance in the accumulation region as well as high-k value, and low barrier height. In addition, the C-V and G/?-V measurements carried out in the frequency range of 20 kHz to 1 MHz were analyzed to understand the effect of frequency on the series resistance Rs and interface states Dit. The measured and calculated results reveal a significant influence of frequency on both Rs and Dit of the fabricated MOS capacitor characteristics.
  • Küçük Resim
    Öğe
    Effect of high-radiation-dose-induced structural modifications of HfSiO4/n-Si on electrical characteristics
    (Pergamon-Elsevier Science Ltd, 2022) Kahraman, Ayşegül; Mutale, Alex; Lök, Ramazan; Yılmaz, Ercan
    High-k/n-Si structures were formed with HfSiO4 films annealed at the temperature range of RT (room temperature)-900 degrees C and radiation-induced structural modifications were determined by XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy) techniques in the study. The effect of oxygen-deficient bond contents on the electrical characteristics of HfSiO4 pMOS (n type Metal Oxide Semiconductor) capacitors whose radiation response was investigated in the 0-50 kGy dose range was investigated. While no XRD peak was observed before and after irradiation at RT and 500 degrees C-HfSiO4/n-Si, crystallization started with irradiation at 900 degrees C. The dielectric constant of the film was found in the range of 16-23. It was determined that Hf-Hf oxygen-deficient bonds act as negative charge trapping centers, while Hf-Si and Si-Si oxygen-defective bonds act as positive charge trapping centers. The direction of the C-V (Capacitance-Voltage) curve changed continuously with increasing radiation dose. The change in the interface trap charge density was found to be higher than the change in the oxide trap charge density for all doses in RT-HfSiO4 pMOS capacitor and for 1 kGy at 500 degrees C-HfSiO4 pMOS capacitor. Oxygen defective bond content and Hf-O-Si/Si-O-Si ratios were sufficient to establish a link between structural analyses and electrical characteristics at some doses. In some cases, the frequency-dependent charges had a more dominant effect on the radiation response of the device compared to the oxide trap charges.
  • Küçük Resim
    Öğe
    Investigation of annealing temperature and gamma irradiation on HfO2/Dy2O3/Al2O3/n-Si (100) memory capacitor
    (Institute of Electrical and Electronics Engineers Inc., 2023) Chirwa, Racheal; Mutale, Alex; Yılmaz, Ercan
    The effect of annealing temperature and gamma irradiation on Al/HfO2/Dy2O3/Al2O3/n-Si (100) tri-layer capacitors have been studied intensively. The HfO2/Dy2O3/Al2O3 were fabricated by using both RF magnetron sputtering and E-beam evaporation techniques, respectively. The samples were annealed at 300oC, 500oC,700oC, and 900oC in N2 ambient for 40min. The device annealed at 700oC had a large memory window of 8.22V under sweeping voltage ±12V compared to other annealed devices. This is attributed to the excellent charge storage capability of the device. Thereafter, this device was exposed to gamma irradiation at various doses of 4 Gy to 16 Gy. C-V and Gm/-V measurements were performed before and after irradiation at 1MHz. The C-V curves shifted toward the positive voltage side. This could be related to the oxide-trapped and interface-trapped charges generated during irradiation © 2023 IEEE.
  • Küçük Resim Yok
    Öğe
    Silicon nano-wire fabrication and its applications
    (Bolu Abant İzzet Baysal Üniversitesi, 2021) Mutale, Alex; Yılmaz, Ercan
    Bu tez, silikon nanotellerin imalatına ve bunların MOS kapasitör olarak uygulamalarına odaklanmaktadır. Silikon nanoteller (SiNW'ler) metal yardımlı kimyasal aşındırma methodu (MACE) kullanılarak üretildi ve işlem sırasında prekursör olarak AgNO3, HF ve H2O2 kullanıldı. Silikon nanoteller, üç farklı silikon alttaş örnekleri kullanılarak üretildi ve HF/H2O2/H2O içinde 10 dakika, 30 dakika ve 60 dakika boyunca aşındırıldı. Daha sonra SiO2, n-Si (100) ve SiNWs/n-Si (100) alt taşlar üzerine kuru ve ıslak oksidasyon yöntemleri kullanılarak 1000°C'de 30 dakika boyunca difüzyon fırınında büyütüldü. SiNW'ler ve SiO2/SiNW'lerin kristal yapıları ve yüzey morfolojileri, x-ışını kırınımı (XRD) ve taramalı elektron mikroskobu (SEM) tekniği ile araştırıldı. Kapasitörlerin elektriksel özelliklerini araştırmak için 1MHz'de SiNW'siz MOS kapasitör ve 1µm, 2µm ve 4µm uzunlukları için SiNW kapasitörlerin kapasitans-voltaj(C-V) ölçümleri yapılmıştır. SiNW'leri olmayan MOS kapasitör, en yüksek kapasitans değerine ve yaklaşık 4.18'lik hesaplanan en yüksek dielektrik sabit değerine sahip olduğu bulundu. Bununla birlikte, SiNW kapasitör uzunluğunun artmasıyla birikim bölgesindeki oksit kapasitansının değeri azalmıştır. 1µm SiNWs kapasitör en uygun değer olarak seçilmiştir çünkü bu kapasitör diğer SiNWs kapasitörlere kıyasla en yüksek oksit kapasitansına ve yüksek k değerine sahiptir. Bu nedenle bu kapasitör 1Gy ile 40Gy arasında değişen farklı dozlarda gama ışını kaynağı kullanılarak ışınlanmıştır. Radyasyon dozu arttıkça kapasitans değerinin arttığı tespit edildi. Ayrıca, sonuçlar, gama ışıması sırasında ara yüzey durumlarının yoğunluk(Dit), oksit tuzak yükler yoğunluğu(?Not) ve ara yüzey tuzak yüklerinin ?Nit indüklendiğini göstermiştir.