DFT çalışması: Katkısız ve kobalt katkılı (8,0), (10,0) tek duvarlı karbon nanotüplerin elektronik ve manyetik özellikleri

Öz

Bu çalışmada, katkısız ve kobalt (Co) katkılı zigzag (8,0) ve (10,0) tek duvarlı karbon nanotüplerin (SWCNT) elektronik ve manyetik özellikleri yoğunluk fonksiyonel teorisi (DFT) çerçevesinde sistematik olarak incelenmiştir. Çalışmada, Co katkısının nanotüplerin bant yapısı, durum yoğunluğu (DOS), Fermi seviyesi ve manyetik moment üzerindeki etkileri karşılaştırmalı olarak analiz edilmiştir. Elde edilen sonuçlara göre, katkısız (8,0) ve (10,0) SWCNT’ler sırasıyla 0.56 eV ve 0.82 eV bant aralıklarına sahip yarı iletken karakterdedir. Co katkısı, bu sistemlerin bant aralıklarını tamamen ortadan kaldırarak yarı iletken–metalik geçişe neden olmuştur. Ayrıca, Co katkılı CNT’lerde Fermi seviyesi çevresinde belirgin bir toplam durum yoğunluğu (TDOS) artışı gözlenmiş, bu da metallic davranış kazandırmıştır. Manyetik özellikler açısından, (8,0) Co katkılı SWCNT’de manyetik sönümleme (quenching) gözlenmiş ve toplam manyetik moment 0 μB olarak hesaplanmıştır. Buna karşılık, (10,0) Co katkılı sistemde toplam momentin ~0.6 μB olduğu belirlenmiştir. Bu fark, Co’nun 3d orbitalleri ile karbonun 2p orbitalleri arasındaki p-d hibritleşme derecesinin tüp çapına bağlı olarak değişmesiyle açıklanmıştır. (10,0) sisteminde spin-up ve spin-down kanalları arasında dengesizlik oluşmuş ve sistem ferromanyetik-metal karakter kazanmıştır. Sonuç olarak, Co katkısının CNT’lerin elektronik yapısını köklü biçimde değiştirdiği, bant boşluğunu ortadan kaldırdığı ve belirli geometrilerde (özellikle (10,0) tüpünde) ferromanyetik davranış oluşturduğu tespit edilmiştir. Bu bulgular, Co katkılı CNT sistemlerinin spintronik, sensör ve nanoelektronik uygulamalarda potansiyel malzemeler olarak değerlendirilebileceğini göstermektedir.

Anahtar Kelimeler

• Karbon nanotüp (CNT)
• Kobalt katkılama
• Elektronik ve manyetik özellikler

DFT study: Electronic and magnetic properties of pristine and cobalt-doped (8,0), (10,0) single-walled carbon nanotubes

Öz

In this study, the electronic and magnetic properties of pristine and cobalt (Co)-doped zigzag (8,0) and (10,0) single-walled carbon nanotubes (SWCNTs) were systematically investigated within the framework of density functional theory (DFT). The effects of Co doping on the band structure, density of states (DOS), Fermi level, and magnetic moment of the nanotubes were comparatively analyzed. The obtained results show that pristine (8,0) and (10,0) SWCNTs exhibit semiconducting characteristics with band gaps of 0.56 eV and 0.82 eV, respectively. Co doping completely eliminates these band gaps, resulting in a semiconductor-to-metal transition. In addition, a notable increase in the total density of states (TDOS) near the Fermi level was observed in Co-doped CNTs, which leads to metallic behavior. From a magnetic perspective, magnetic quenching was observed in the (8,0) Co-doped SWCNT, where the total magnetic moment was calculated as 0 μB. Conversely, the (10,0) Co-doped system exhibited a total magnetic moment of approximately 0.6 μB. This difference is attributed to the variation in the degree of p–d hybridization between Co 3d orbitals and C 2p orbitals depending on the tube diameter. In the (10,0) system, an imbalance between spin-up and spin-down channels emerged, giving the system a ferromagnetic metallic character. In conclusion, Co doping profoundly alters the electronic structure of CNTs by eliminating the band gap and inducing ferromagnetic behavior, particularly in the (10,0) configuration. These findings indicate that Co-doped CNT systems can be considered as promising materials for spintronic, sensor, and nanoelectronic applications.

Anahtar Kelimeler

• Carbon nanotube (CNT)
• Cobalt doping
• Electronic and magnetic properties

Kaynakça

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