TY - JOUR
T1 - Tuning the Electronic and Magnetic Properties of Nitrogen-Functionalized Few-Layered Graphene Nanoflakes
AU - Soin, Navneet
AU - Ray, Sekhar C.
AU - Sarma, Sweety
AU - Mazumder, Debarati
AU - Sharma, Surbhi
AU - Wang, Yu Fu
AU - Pong, Way Faung
AU - Roy, Susanta Sinha
AU - Strydom, André M.
PY - 2017/6/7
Y1 - 2017/6/7
N2 - In this article, we report the modification of the electronic and magnetic properties of few-layered graphene (FLG) nanoflakes by nitrogen functionalization carried out using radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) and electron cyclotron resonance (ECR) plasma processes. Even though the rf-PECVD N 2 treatment led to higher N-doping levels in the FLG (4.06 atomic %) as compared to the ECR process (2.18 atomic %), the ferromagnetic behavior of the ECR FLG (118.62 × 10 -4 emu/g) was significantly higher than that of the rf-PECVD FLG (0.39 × 10 -4 emu/g) and pristine graphene (3.47 × 10 -4 emu/g). Although both plasma processes introduce electron-donating N atoms into the graphene structure, distinct dominant nitrogen bonding configurations (pyridinic, pyrrolic) were observed for the two FLG types. Whereas the ECR plasma introduced more sp 2 -type nitrogen moieties, the rf-PECVD process led to the formation of sp 3 -coordinated nitrogen functionalities, as confirmed through Raman measurements. The samples were further characterized using X-ray absorption near-edge spectroscopy (XANES), and X-ray and ultraviolet photoelectron spectroscopies revealed an increased electronic density of states and a significantly higher concentration of pyrrolic groups in the rf-PECVD samples. Because of the formation of reactive edge structures and pyridinic nitrogen moieties, the ECR-functionalized FLG samples exhibited highest saturation magnetization behavior with the lowest field hysteretic features. In comparison, the rf-PECVD samples displayed the lowest saturation magnetization owing to the disappearance of magnetic edge states and formation of stable nonradical-type defects in the pyrrole type structures. Our experimental results thus provide new evidence regarding the control of the magnetic and electronic properties of few-layered graphene nanoflakes through control of the plasma-processing route.
AB - In this article, we report the modification of the electronic and magnetic properties of few-layered graphene (FLG) nanoflakes by nitrogen functionalization carried out using radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) and electron cyclotron resonance (ECR) plasma processes. Even though the rf-PECVD N 2 treatment led to higher N-doping levels in the FLG (4.06 atomic %) as compared to the ECR process (2.18 atomic %), the ferromagnetic behavior of the ECR FLG (118.62 × 10 -4 emu/g) was significantly higher than that of the rf-PECVD FLG (0.39 × 10 -4 emu/g) and pristine graphene (3.47 × 10 -4 emu/g). Although both plasma processes introduce electron-donating N atoms into the graphene structure, distinct dominant nitrogen bonding configurations (pyridinic, pyrrolic) were observed for the two FLG types. Whereas the ECR plasma introduced more sp 2 -type nitrogen moieties, the rf-PECVD process led to the formation of sp 3 -coordinated nitrogen functionalities, as confirmed through Raman measurements. The samples were further characterized using X-ray absorption near-edge spectroscopy (XANES), and X-ray and ultraviolet photoelectron spectroscopies revealed an increased electronic density of states and a significantly higher concentration of pyrrolic groups in the rf-PECVD samples. Because of the formation of reactive edge structures and pyridinic nitrogen moieties, the ECR-functionalized FLG samples exhibited highest saturation magnetization behavior with the lowest field hysteretic features. In comparison, the rf-PECVD samples displayed the lowest saturation magnetization owing to the disappearance of magnetic edge states and formation of stable nonradical-type defects in the pyrrole type structures. Our experimental results thus provide new evidence regarding the control of the magnetic and electronic properties of few-layered graphene nanoflakes through control of the plasma-processing route.
UR - http://www.scopus.com/inward/record.url?scp=85024472846&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.7b01645
DO - 10.1021/acs.jpcc.7b01645
M3 - Article
AN - SCOPUS:85024472846
SN - 1932-7447
VL - 121
SP - 14073
EP - 14082
JO - Journal Of Physical Chemistry C
JF - Journal Of Physical Chemistry C
IS - 26
ER -