بررسي ساختار الكتروني، خواص مغناطيسي و اپتيكي نيم‌رسانايSn1-xCoxO2 با استفاده از نظريۀ تابعي چگالي

Study of Electronic Structure, Magnetic and Optical Properties of Sn1-xCoxO2 Semiconductors using Density Functional Theory

در اﯾﻦ ﻣﻘﺎﻟﻪ ﺳﺎﺧﺘﺎراﻟﮑﺘﺮوﻧﯽ و ﺧﻮاص ﻣﻐﻨﺎﻃﯿﺴﯽ و اﭘﺘﯿﮑﯽ ﻧﻤﻮﻧﻪﻫﺎي ﺧﺎﻟﺺ SnO2 و آﻻﯾﯿﺪة Sn1-xCoxO2 )0/1875 ،0/125 ،0/0625 و x=0/25( ﺑﺎ اﺳﺘﻔﺎده از ﻧﻈﺮﯾﮥ ﺗﺎﺑﻌﯽ ﭼﮕﺎﻟﯽ ﺑﺮرﺳﯽ ﻣﯽﺷﻮﻧﺪ. اﺛﺮ ﺗﻬﯽ ﺟﺎي اﮐﺴﯿﮋن روي ﺧﻮاص ﺳﺎﺧﺘﺎري و ﻣﻐﻨﺎﻃﯿﺴﯽ ﻧﻤﻮﻧﻪﻫﺎ ﻧﯿﺰ ﺑﺮرﺳﯽ ﺷﺪ. ﺑﺎ ﺑﺮرﺳﯽ ﺧﻮاص ﻣﻐﻨﺎﻃﯿﺴﯽ ﻧﻤﻮﻧﻪﻫﺎي آﻻﯾﯿﺪه ﻣﺸﺨﺺ ﺷﺪ ﮐﻪ اﻓﺰاﯾﺶ ﻏﻠﻈﺖ آﻻﯾﺶ ﺳﺒﺐ اﻓﺰاﯾﺶ ﭼﮕﺎﻟﯽ ﺗﺮازﻫﺎي اﻧﺮژي ﻣﺮﺑﻮط ﺑﻪ اورﺑﯿﺘﺎلﻫﺎي Co-3d در ﻧﺰدﯾﮑﯽ ﺗﺮاز ﻓﺮﻣﯽ ﻣﯽﺷﻮد. ﺑﺮرﺳﯽ ﻓﺎز ﭘﺎﯾﺪار ﻣﻐﻨﺎﻃﯿﺴﯽ ﻧﻤﻮﻧﻪﻫﺎي آﻻﯾﯿﺪه ﻧﺸﺎن داد ﮐﻪ در آﻻﯾﺶﻫﺎي 12/5% و 25% ﻓﺎز ﭘﺎﯾﺪار ﺷﺒﮑﻪ ﻓﺮوﻣﻐﻨﺎﻃﯿﺲ اﺳﺖ. ﺣﻀﻮر ﺗﻬﯽﺟﺎي اﮐﺴﯿﮋن در ﻧﻤﻮﻧﮥ ﻓﺮوﻣﻐﻨﺎﻃﯿﺴﯽ Sn0.875Co0.125O0.9375 ﻧﺰدﯾﮏ ﺑﻪ ﯾﻮن ﮐﺒﺎﻟﺖ ﻣﻨﺠﺮ ﺑﻪ اﻓﺰاﯾﺶ ﮔﺸﺘﺎور ﻣﻐﻨﺎﻃﯿﺴﯽ ﯾﻮنﻫﺎي ﮐﺒﺎﻟﺖ ﻣﯽﺷﻮد. ﺑﺮرﺳﯽ ﺧﻮاص اﭘﺘﯿﮑﯽ ﻧﻤﻮﻧﮥ ﺧﺎﻟﺺ و ﻧﻤﻮﻧﻪﻫﺎي آﻻﯾﯿﺪه ﺑﺎ 12/5 ،%6/25% و 25% ﮐﺒﺎﻟﺖ ﻧﺸﺎن داد ﮐﻪ ﺑﺎ اﻓﺰاﯾﺶ ﻏﻠﻈﺖ آﻻﯾﺶ ﺗﺎ 12/5%، ﮔﺎف ﻧﻮاري اﭘﺘﯿﮑﯽ ﮐﺎﻫﺶ و ﺳﭙﺲ ﺑﺎ اﻓﺰاﯾﺶ ﺑﯿﺶﺗﺮ آن ﺗﺎ 25%، ﮔﺎف ﻧﻮاري اﭘﺘﯿﮑﯽ اﻓﺰاﯾﺶ ﻣﯽﯾﺎﺑﺪ. ﺑﺎ اﻓﺰاﯾﺶ آﻻﯾﺶ ﺗﺎ 12/5%، ﺷﺪت ﻣﺮﺑﻮط ﺑﻪ اوﻟﯿﻦ ﻗﻠﻪﻫﺎ در ﻃﯿﻒ ﺗﺎﺑﻊ دياﻟﮑﺘﺮﯾﮏ ﻧﻤﻮﻧﻪﻫﺎ، ﻫﻢﭼﻨﯿﻦ ﺿﺮاﯾﺐ درآﺷﺎﻣﯽ و ﺧﺎﻣﻮﺷﯽ اﻓﺰاﯾﺶ و ﺷﺪت ﻣﺮﺑﻮط ﺑﻪ ﻗﻠﻪﻫﺎي ﻇﺎﻫﺮ ﺷﺪه در ﻣﺤﺪودة اﻧﺮژيﻫﺎي ﺑﺎﻻﺗﺮ از6eV ﮐﺎﻫﺶ ﻣﯽﯾﺎﺑﻨﺪ. ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﻃﯿﻒﻫﺎي ﺑﺎزﺗﺎﺑﻨﺪﮔﯽ و ﺿﺮﯾﺐ درآﺷﺎﻣﯽ ﻣﺸﺨﺺ ﺷﺪ ﮐﻪ ﺑﺎ اﻓﺰاﯾﺶ ﻏﻠﻈﺖ آﻻﯾﺶ ﺗﺎ 12/5% ﻣﯿﺰان ﻋﺒﻮر ﻓﻮﺗﻮن در ﻧﺎﺣﯿﮥ ﻣﺮﺋﯽ ﮐﺎﻫﺶ ﻣﯽﯾﺎﺑﺪ.

In this paper electronic structure, magnetic and optical properties of pure SnO2 and Sn1-xCoxO2 (x= 6.25%, 12.5%, 18.75% and 25%) samples and effect of Oxygen vacancies on those were investigated using density functional theory (DFT). Density of states and band structure curves show Co doping causes increase in energy surfaces near to the Fermi level. The results of this study showed the ground states of the 12.5% and 25% samples were ferromagnetic. The study of the effects of Oxygen vacancy on 12.5%Co doped- sample revealed that the introducing of vacancies causes increase in magnetic moment of the Co ions. The results were also showed that by increasing the Co concentration up to 12.5% the optical band gap decreases and then by more increasing of Co it increases. The intensity of the first peak in absorption curve increases and the intensity of the other peak above the 6eV decreases. The red shift of peak positions was also observed on absorption curves with increasing Co concentration to 12.5%.