Applied Surface Science 332 (2015) 147–151 Contents lists available at ScienceDirect Applied Surface Science jou rn al h om ep age: www.elsevier.com/locate/apsusc A first-principles study of n-type and p-type doping of germanium carbide sheet A.G. Gökc ¸ e a,b,∗ , E. Aktürk b,∗∗ a Department of Physics, Dokuz Eylül University, 35160 ˙ Izmir, Turkey b Department of Physics, Adnan Menderes University, 09100 Aydın, Turkey a r t i c l e i n f o Article history: Received 23 November 2014 Received in revised form 19 January 2015 Accepted 19 January 2015 Available online 28 January 2015 PACS: 71.15.Mb 73.20.At 73.22.-f 73.90.+f 75.70.Ak Keywords: Germanium carbide monolayer n-Type and p-type doping Adsorption Density functional theory a b s t r a c t We present our study on the adsorption of C, Si and Ge adatoms on binary compound germanium carbide (GeC) honeycomb structure based on density functional theory using the generalized gradient approxi- mation. We found that C atom is bound at bridge site, while Si and Ge prefer to adsorb to top site above the top of carbon. The electronic and magnetic properties of GeC can be modified by the adsorption of these adatoms. Nonmagnetic semiconductor GeC is either metal or narrow band gap semiconductor depending on the adatoms coverage. One of the reason of this effect is the bonding combination of adatom-p and GeC-sp 2 orbitals. All the adatom adsorptions on GeC have zero net magnetic moment, except Ge adsorp- tion at low coverage, which has a net magnetic moment of  = 2.0 B per cell. Our results also indicate that because of the charge transfer, the adsorption of C and Si/Ge on a GeC surface allow us to obtain p- and n-type doping, respectively. Therefore, adatom covered GeC can serve as an interesting alternative for the nanodevice applications. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Graphene, a monoatomic layer of carbon atoms arranged in a two-dimensional (2D) honeycomb lattice, was first isolated from bulk graphite by Novoselov et al. [1]. Graphene exhibits outstand- ing electronic, thermal, optical and mechanical properties, such as massless Dirac fermions [2], high thermal conductivity [3,4], half- integer Hall conductance [5,6], high optical transmittance [7,8], high carrier mobility at room temperature [9], high chemical stabil- ity, ambipolar electric field effect [10] and extraordinary stiffness [11]. All these exotic properties of graphene have led to investi- gation of other 2D honeycomb lattices such as hexagonal boron nitrides [12], zinc oxide [13] and transition metal dichalcogenides [14]. Especially, graphene-like buckled honeycomb structures of silicene and germanene [15] have attained significant interest due to their nonmagnetic semimetallic behavior with linearly crossing ∗ Corresponding author at: Department of Physics, Dokuz Eylül University, 35160 ˙ Izmir, Turkey. Tel.: +90 2323018673; fax: +90 2324534188. ∗∗ Corresponding author. Tel.: +90 2562130835x1894; fax: +90 2562135379. E-mail addresses: aytac.gokce@deu.edu.tr (A.G. Gökc ¸ e), ethem.akturk@adu.edu.tr (E. Aktürk).  and  * bands at Fermi level which is similar to graphene and due to their compatibility with silicon-based micro-electronic industry. In addition, two-dimensional silicon carbide (SiC) and germanium carbide (GeC) honeycomb structures have been reported theo- retically as stable [16–19]. In contrast to the zero band gap of honeycomb lattices of group-IV elements, monolayer honeycomb structures of group-IV binary compounds such as 1H-GeC and 1H- SiC are direct and indirect band gap semiconductors, respectively [17]. As a result of direct band gap properties, 1H-GeC can be promising material for digital circuits and light-emitting diodes. After determining its 2D honeycomb structure as stable [17], the mechanical [20] and electronic [21,22] properties of GeC were investigated. It was found that the electronic properties of 1H- GeC can be modified by introducing various strained conditions [23]. Another study on semifluorinated and semihydrogenated GeC sheets showed that by controlling the adsorption atoms, the elec- tronic and magnetic properties can be modulated [24]. Earlier studies dealing with functionalization of graphene [25,26], sil- icene [27] and germanene [28] have shown that the electronic and magnetic properties of graphene and silicene can be remarkably changed upon adatom adsorption as well. In our previous study [25,29], we found that Si, Ge and C are bound to graphene with significant binding energies, and hence these adatoms give rise http://dx.doi.org/10.1016/j.apsusc.2015.01.146 0169-4332/© 2015 Elsevier B.V. All rights reserved.