Send Orders for Reprints to reprints@benthamscience.net Current Nanoscience, 2015, 11, 87-94 87 Analytical Study of Electronic Structure in Archimedean Type-Spiral Zig-Zag Graphene Nanoscroll Afiq Hamzah 1 , Mohammad Taghi Ahmadi 1,2 and Razali Ismail 1, * 1 Computational Nanoelectronic Research Group, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 Johor, Malaysia; 2 Nanotechnology Research Center Nanoelectronic Group, Physics Department, Urmia University, 57147 Urmia, Iran Abstract: The semiconducting electronic properties of graphene nanoscroll (GNS) are very much related to its geometric structure. The aim of this study is to construct a GNS energy dispersion model within low-energy transport of 1 eV in identifying its electronic properties and carrier statistics. Non-parabolic energy dispersion is used to incorporate the Ar- chimedean type-spiral model, and the band gap is assessed based on chirality and geometry effects. The energy band within low-energy transport indicates that GNS can achieve a quantum conductance limit of 6.45 k for ballistic trans- port. On the other hand, the numbers for three minimum sub-bands are attained based on non-parabolic energy dispersion, and the semi-metallic zig-zag GNS is found at chirality (3j + 1, 0). This work consistently predicts the semiconducting properties of the tight-binding model from previous work. The GNS overlapping region strongly affects its electronic properties. Constantly increasing the length of the overlapping region decreases the band gap exponentially, whilst semi- metallic GNS forms when the overlap reaches a certain limit. The carrier density with temperature dependence is subse- quently assessed at the intrinsic level, and found that the number of carriers in GNS shows a higher rate of increment (ex- ponentially) compared to carbon nanotubes (CNT), in accordance to their diameter. The results are very useful in giving an intuitive understanding on GNS carrier statistics as subject to geometry changes. Keywords: Band gap, chirality, graphene nanoscroll, intrinsic carrier density, low-energy transport, overlapping region. 1. INTRODUCTION Carbon-based materials show promising features as cata- lyst in comprehending Moore’s Law, and in the field of nanotechnology, which prompts for an innovative outlook when confronted with new challenges in various situations. Carbon Nanotube (CNT) is one of the carbon allotropes. It is described as a closed-edge hollow cylindrical structure hav- ing a diameter confined to one-dimension (1D). This feature makes the material scientifically interesting for future tech- nology appliances such as Ultra Large Scale Design (ULSI) [1], sensors, mechanical actuators and even as drugs carriers. It is naturally constructed from the sp 2 hybridized atom model, welded by a strong  bond, instigating to superior mechanical properties and electromigration resistance with the capability to operate within the quantum conductance limit of 6.45 k [2-5]. However, the ability to control its band gap and number of nanotube walls has remained prob- lematic [6]. Graphene Nanoscroll (GNS) is another form of carbon allotrope that is synthesized by rolling a graphene sheet. However unlike CNT, GNS allows a band gap, which is con- trolled via an overlapping region [7-9]. GNS can also be described as an Archimedean type spiral graphene structure, due to its spiral configuration that is open along the edge of *Address correspondence to this author at the Computational Nanoelec- tronic Research Group, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 Johor, Malaysia; Tel: + 6075535222; Fax: + 607-5566272; E-mail: razali@fke.utm.my its translational axis, as shown in Fig. (1). It was initially described in the 60s by Bacon as a scroll whisker carbon [10]. Later in 2003, a simple low temperature chemical route offered a less-expensive method in producing larger quanti- ties of scroll graphene. The results indicated that the forma- tion of GNS is influenced by elastic bending energy and Van der Waals (VDW) interactions at the overlapping region [9] as both energies compensate for each other to form a stable GNS structure. They have the same nomenclature as CNT, where the electronic structure is determined by chirality. These structures consist of zig-zag GNS (ZGNS), armchair GNS (AGNS) and chiral GNS [11, 12]. Although CNT and GNS can be defined by the same nomenclature, their struc- tures remain distinct as GNS exhibits tunable overlapping layers in controlling the band gap. This has also led to more discoveries on its structural electronic properties, where ab initio study has theoretically proved that the properties of GNS change from semiconductor to metallic by increasing the overlapping region to a certain value. This implies great dependency of its electronic properties on its geometrical structure [11-15]. The understanding of the electronic properties of GNS can be deliberated using band dispersion of the Nearest Neighbor Tight Binding (NNTB) model in order to provide the information at the Dirac cone of the graphene band struc- ture, where the band gap can be assessed. Chen et al., (2007) actively working on GNS, have used the Molecular Dynamic Simulation (MDS) in examining its band dispersion by dis- tinguishing the electronic properties based on its chirality, 1875-6786/15 $58.00+.00 © 2015 Bentham Science Publishers