Pekik Nurwantoro
Jurusan Fisika, Universitas Gadjah Mada, Yogyakarta

Published : 5 Documents
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Effect of Substrate Temperature and Target-Substrate Distance on Growth of TiO2 Thin Films by Using DC- Reactive Sputtering Technique Rabih, Laith; -, Sudjatmoko; Triyana, Kuwat; Nurwantoro, Pekik
Jurnal Fisika Indonesia Vol 17, No 49 (2013)
Publisher : Department of Physics Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1097.161 KB) | DOI: 10.22146/jfi.24408

Abstract

Titanium oxide (TiO2) thin films have been deposited by a DC sputtering technique onto microscope glass slides. The effect of substrate temperature (Ts) and target-substrate distance (Dts) on some optical and electrical properties have been studied each individually. The structure of TiO2 thin films has been improved and became more crystalline when Ts has been increased (from 150 ºC to 250 ºC). The conductivity (?), deposition rate (DR) and average values of grain size (G.S) have been increased with increasing Ts while the values of band gap (Eg) and weight percentage of the anatase phase (WA) have been decreased. The thickness of TiO2 film has been increased from 920 nm to 960 nm with increase Ts while it has been decreased from 960 nm to 680 nm with increase Dts (from 25mm to 35mm). As Dts has been increased, the conductivity ?, thickness (d) and average values of grain size have been decreased. The decreasing of conductivity at Dts=35 maybe attributes to increase the weight percentage of the rutile phase (WR). The XRD results show that the TiO2 structure phase has been varied. The results show that the optical and electrical properties of TiO2 film affected by changes the condition parameters especially Ts and Dts as well as the density and energy of the impinging atoms. The surface morphology and component of TiO2 thin films, resistance, optical transmittance and structure of film were characterized by SEM (EDX), I-V meter, UV-VIS spectrophotometer and XRD respectively.
Density-Functional-Theory Calculations of Formation Energy of the Nitrogen-Doped Diamond Sholihun, Sholihun; Kadarisman, Hana Pratiwi; Nurwantoro, Pekik
Indonesian Journal of Chemistry Vol 18, No 4 (2018)
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (479.137 KB) | DOI: 10.22146/ijc.26785

Abstract

The geometry optimization of the nitrogen-doped diamond has been carried out by the density functional theory (DFT) calculations. We model the defective diamond of substitutional and interstitial nitrogen atoms by using a simple-cubic supercell. Atoms in the supercell are relaxed by allowing them to move so that the atomic forces are less than 5.0 × 10-3 eV/Å. We calculate the formation energy for substitutional and interstitial sites. We find that the formation energy for the substitutional defect is10.89 eV. We check the convergence of the calculation with respect to the k×k×k - Monkhorst-Pack grids. We show that the energy difference between k = 4 and 6 is very small (7.0 meV). We also check the calculations by using a 216-sites supercell and find that the energy difference is 0.10 eV. Thus, the calculations of the formation energy converge well. As for the interstitial defect, we model some possible configurations and find that the smallest formation energy is 21.88 eV. Therefore, the most stable configuration of the nitrogen-doped diamond belongs to the substitutional site.
Introducing Undergraduate Students to Nonlinear Dynamics through A Numerical Approach Nugroho, Fahrudin; Azhari, Irfan Taufiq; Yusuf, Yusril; Nurwantoro, Pekik
Omega: Jurnal Fisika dan Pendidikan Fisika Vol 4 No 2 (2018)
Publisher : Program Studi Pendidikan Fisika UHAMKA

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31758/OmegaJPhysPhysEduc.v4i2.45

Abstract

This paper describes a numerical method that used to solve the nonlinear Schr\"{o}dinger equation. The methods are an exponential time differencing method and a spectral method. The result indicates that at a certain parameter, fluctuation of wave function has contained chaotic dynamics. This case is expected to be used as an example for introducing numerical methods to undergraduate students on nonlinear dynamics. This introduction is deemed necessary, referring to the curriculum and syllabus used in several educational institutions in various countries that have included the topic of nonlinearity.
Simulasi Komputer Pengaruh Efek Proksimitas pada Medan Kritis Superkonduktor Anwar, Fuad; Nurwantoro, Pekik; Hermanto, Arief
Risalah Fisika Vol 1, No 2 (2017): Risalah Fisika ISSN 2548-9011
Publisher : Physical Society of Indonesia (PSI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (368.304 KB) | DOI: 10.35895/rf.v1i2.21

Abstract

Telah dibuat kajian pengaruh syarat batas efek proksimitas pada penyelesaian komputasi persamaan Ginzburg-Landau Gayut Waktu. Bahan kajian adalah superkonduktor berbentuk kotak yang berbatasan dengan bahan lain pada keempat sisinya dan dipengaruhi medan magnet luar. Metode pembuatan simulasi didasarkan pada persamaan Ginzburg-Landau gayut waktu serta persamaan syarat batas parameter benahan dan syarat batas medan magnet. Persamaan-persamaan tersebut lalu didiskretkan dengan menggunakan metode yU. Hasil kajian menunjukkan bahwa nilai medan kritis permukaan membesar, medan kritis rendah mengecil pada ukuran bahan Nx×Ny = 12×12 dan membesar pada ukuran bahan Nx×Ny = 32×32 jika nilai panjang ekstrapolasi membesar. Kata kunci: efek proksimitas, persamaan TDGL, superkonduktor
KAJIAN KOMPUTASI ALGORITMA KUANTUM QUANTUM V ARIATIONAL EIGENSOLVER UNTUK SIMULASI MOLEKUL H2 Rahmat, M Sidik Augi; Nurwantoro, Pekik
Jurnal Fisika Indonesia Vol 24, No 1 (2020)
Publisher : Department of Physics Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jfi.v24i1.52011

Abstract

Telah dilakukan telaah teoritis dan komputasi mengenai algoritma kuantum variational quantum eigensolver simulasi molekul H2. Algoritma variational quantum eigensolver (VQE) adalah salah satu algoritma yang dapat diterapkan pada komputer kuantum sederhana pada masa kini dan merupakan algoritma yang cukup stabil dan efek dekoherensi. Algoritma VQE disebut sebagai hybrid quantum-classical karena sebagian algoritma dikerjakan pada komputer klasik. Prinsip dasar algoritma VQE adalah prinsip variasi, yaitu pencarian fungsi gelombang yang akan mengakibatkan energi sistem kuantum memiliki energi terendah. Fungsi gelombang dan Hamiltonan pada algoritma VQE disimulasikan dengan menggunakan gerbang-gerbang kuantum. Untuk dapat dioperasikan oleh gerbang kuantum. Hamiltonan dan fungsi gelombang pada penelitian ini menggunakan wakilan kuantisasi kedua. Penelitian ini menggunakan transformasi Jordan-Wigner dan Bravyi-Kitaev dari operator fermionik menjadi operator kubit (qubit) atau gerbang kuantum.Perhitungan atau komputasi energi sistem dilakukan menggunakan komputer kuantum, namun optimasi dilakukan pada komputer klasik menggunakan algoritma optimasi seperti Nelder-Mead, Powell dan BFGS. Penelitian ini akan mendekati fungsi gelombang sistem dengan beberapa basis fungsi dan metode, kemudian dari hasil yang diperoleh akan dilihat pendekatan seperti apa yang paling cocok untuk simulasi molekul H2. Simulasi numerik pada penelitian ini menggunakan paket pemrograman OpenFermion dan layanan komputasi awan kuantum Rigetti Computing.