Nenohai, Ari June Wilyanto Tyas (2026) Studi Kemagnetan Material Dua Dimensi Menggunakan Metode Simulasi Dinamika Molekuler Dan Kalkulasi Teori Fungsional Kerapatan. Doctoral thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Kajian kemagnetan material dua dimensi penting dalam pengembangan material fungsional untuk aplikasi nanoelektronika dan spintronik. Sifat magnetik pada skala atomik dapat dikendalikan melalui rekayasa defek dan perlakuan temperatur yang memodifikasi struktur elektronik serta distribusi spin. Grafena memiliki mobilitas elektron tinggi, tetapi bersifat semimetal dengan celah pita nol, sedangkan heksagonal boron nitrida (h-BN) merupakan isolator bercelah pita lebar dengan stabilitas termal tinggi. Namun, hubungan antara evolusi struktur akibat temperatur, perubahan sifat elektronik, dan kemagnetan kedua material tersebut masih memerlukan pemahaman atomistik. Penelitian ini bertujuan mengevaluasi pengaruh temperatur terhadap evolusi struktur atomik dan stabilitas konfigurasi defek pada grafena dan h-BN, mengevaluasi konsekuensi perubahan struktur tersebut terhadap sifat elektronik dan magnetik, serta merumuskan mekanisme fisis terpadu yang menghubungkan temperatur, rekonstruksi defek, struktur elektronik, dan momen magnetik melalui integrasi simulasi Molecular Dynamics (MD) dan kalkulasi Density Functional Theory (DFT). Defek kekosongan, antisitus, dan kombinasi keduanya dimodelkan sebagai struktur awal, kemudian dikenai perlakuan temperatur melalui simulasi MD. Struktur hasil evolusi atomik selanjutnya dianalisis dengan DFT terpolarisasi spin. Hasil menunjukkan bahwa grafena murni memiliki celah pita nol dan momen magnetik 0,00 μB/sel. Pada grafena dengan kekosongan, peningkatan temperatur dari 300 K hingga 1000 K memicu rekonstruksi lokal, memodifikasi struktur elektronik, memperkuat pemisahan kanal spin, dan meningkatkan momen magnetik dari 0,01 μB/sel menjadi 2,00 μB/sel. h-BN murni tetap nonmagnetik, dengan celah pita menurun dari 3,67 eV pada 900 K menjadi 3,49 eV pada 1225 K. Antisitus boron menghasilkan celah pita 1,33 – 1,66 eV, sedangkan antisitus nitrogen mempersempitnya menjadi 0,35 – 0,53 eV. Kekosongan boron menghasilkan keadaan elektronik yang lebih terlokalisasi di dalam celah pita dan pemisahan spin lebih kuat dibandingkan dengan kekosongan nitrogen. Kombinasi antisitus boron dan kekosongan boron menunjukkan efek paling dominan, ditandai lokalisasi keadaan di sekitar energi Fermi serta peningkatan momen magnetik dari sekitar 1,00 μB/sel pada 900 K menjadi 3,00 μB/sel pada 1225 K. Secara keseluruhan, integrasi MD dan DFT berhasil mengungkap mekanisme atomistik yang menghubungkan temperatur, evolusi struktur, konfigurasi defek, struktur elektronik, dan kemagnetan. Kekosongan boron, khususnya dalam kombinasi dengan antisitus boron, merupakan konfigurasi paling efektif untuk meningkatkan kemagnetan h-BN, sedangkan kekosongan grafena berhasil menginduksi kemagnetan lokal. Temuan ini memberikan landasan fundamental bagi pengembangan material dua dimensi untuk teknologi spintronik dan nanoelektronika.
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The investigation of magnetism in two-dimensional materials is essential for developing functional materials for nanoelectronic and spintronic applications. At the atomic scale, magnetic properties can be tailored through defect engineering and thermal treatment, which alter the electronic structure and spin distribution. Graphene exhibits high electron mobility but is intrinsically a zero-band-gap semimetal, whereas hexagonal boron nitride (h-BN) is a wide-band-gap insulator with high thermal stability. Nevertheless, the relationship between temperature-induced structural evolution, changes in electronic properties, and magnetism in both materials remains insufficiently understood at the atomistic level. This study aims to evaluate the effect of temperature on the evolution of atomic structure and the stability of defect configurations in graphene and h-BN, assess the consequences of these structural changes on electronic and magnetic properties, and formulate an integrated physical mechanism linking temperature, defect reconstruction, electronic structure, and magnetic moments through the integration of Molecular Dynamics (MD) simulations and Density Functional Theory (DFT) calculations. Vacancy, antisite, and combined defects were introduced into the initial structures and subsequently subjected to thermal treatment using MD simulations. The resulting thermally evolved configurations were then analyzed using spin-polarized DFT. The results show that pristine graphene has a zero band gap and a magnetic moment of 0.00 μB/cell. In vacancy-defected graphene, increasing the temperature from 300 K to 1000 K induces local structural reconstruction, modifies the electronic structure, enhances spin-channel splitting, and increases the magnetic moment from 0.01 μB/cell to 2.00 μB/cell. Pristine h-BN remains nonmagnetic, while its band gap decreases from 3.67 eV at 900 K to 3.49 eV at 1225 K. Boron antisite defects yield band gaps of 1.33 – 1.66 eV, whereas nitrogen antisite defects narrow the gap to 0.35 – 0.53 eV. Boron vacancies generate more strongly localized in-gap states and greater spin splitting than nitrogen vacancies. The configuration combining a boron antisite defect and a boron vacancy exhibits the most pronounced effect, characterized by localized states near the Fermi level and an increase in magnetic moment from approximately 1.00 μB/cell at 900 K to 3.00 μB/cell at 1225 K. Overall, the integrated MD and DFT approach successfully elucidates the atomistic mechanism linking temperature, structural evolution, defect configurations, electronic structure, and magnetism. Boron-vacancy configurations, particularly those combined with boron antisite defects, are the most effective for enhancing magnetism in h-BN, whereas vacancies in graphene induce local magnetism. These findings provide a fundamental basis for the development of two-dimensional materials for spintronic and nanoelectronic technologies.
| Item Type: | Thesis (Doctoral) |
|---|---|
| Uncontrolled Keywords: | grafena, h-BN, dinamika molekuler, teori fungsional kerapatan, rekayasa defek, sifat magnetik. graphene, h-BN, molecular dynamics, density functional theory, defect engineering, magnetic properties |
| Subjects: | Q Science Q Science > QC Physics Q Science > QC Physics > QC 611.97.T46 Temperature effects. Including transition temperature Q Science > QC Physics > QC765 Magnetic materials |
| Divisions: | Faculty of Science and Data Analytics (SCIENTICS) > Physics > 45001-(S3) PhD Thesis |
| Depositing User: | Ari June Wilyanto Tyas Nenohai |
| Date Deposited: | 05 Aug 2026 01:51 |
| Last Modified: | 05 Aug 2026 01:51 |
| URI: | http://repository.its.ac.id/id/eprint/143899 |
Available Versions of this Item
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Studi Kemagnetan Material Dua Dimensi Menggunakan Metode Simulasi Dinamika Molekuler Dan Kalkulasi Teori Fungsional Kerapatan. (deposited 05 Aug 2026 02:04)
- Studi Kemagnetan Material Dua Dimensi Menggunakan Metode Simulasi Dinamika Molekuler Dan Kalkulasi Teori Fungsional Kerapatan. (deposited 05 Aug 2026 01:51) [Currently Displayed]
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