First principles band gap engineering of [1 1 0] oriented 3C-SiC nanowires José Luis Cuevas a,⇑ , Francisco de Santiago a , Jesús Ramírez a , Alejandro Trejo a , Álvaro Miranda a , Luis Antonio Pérez b , Miguel Cruz-Irisson a a Instituto Politécnico Nacional, ESIME-Culhuacán, Av. Santa Ana 1000, 04430 Ciudad de México, Mexico b Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, 01000 Ciudad de México, Mexico article info Article history: Received 6 June 2017 Received in revised form 27 September 2017 Accepted 9 October 2017 Keywords: SiC Nanowires DFT Surface passivation Formation energy abstract Silicon carbide nanowires offer excellent opportunities for technological applications under harsh envi- ronmental conditions, however, the 3C-SiC polytype nanowires, grown along the [1 1 0] crystallographic direction, have been rarely studied, as well as the effects of the surface passivation on their physical prop- erties. This work addresses the effects of hydrogen passivation on the electronic band gap of silicon car- bide nanowires (SiCNWs) grown along the [1 1 0] direction by means of Density Functional Theory. We compare the electronic properties of fully hydrogen-passivated SiCNWs in comparison to those of SiCNWs with a mixed passivation of oxygen and hydrogen by changing some of the surface dihydrides with SiAOASi or CAOAC bonds. The results show that regardless of the diameter and passivation, most of the nanowires have a direct band gap which suggests an increased optical activity. The surface CAOAC bonds reduce the electronic band gap energy compared to that of the fully H-terminated phase, while the nanowires with SiAOASi bonds have a larger band gap. The calculation of formation energies shows that the oxygen increases the chemical stability of the SiCNWs. These results indicate the possibility of band gap engineering on SiC nanostructures through surface passivation. Ó 2017 Elsevier B.V. All rights reserved. 1. Introduction Silicon carbide is an interesting material that has attracted much attention due to its properties such as chemical inertness, high hardness (9.5 mhos) and large band gap that make it suitable for applications on electronic devices operating under harsh condi- tions of high frequency, temperature and electrical currents[1,2]. It is well known that SiC has more than 200 polytypes [3,4], but only the hexagonal ones 2H, 4H, and 6H have been extensively studied due to their excellent thermal and electronic properties [5,6].On the other hand, the 3C-SiC polytype is the most attractive for elec- tronics due to its highest electron mobility amongst all of the other polytypes [7], and its possible use in MEMS grown on Si [8]. Besides, it has been observed that after annealing heat treatments, or by an applied shear stress, some hexagonal polytypes, especially the 2H one can easily transform into other polytypes, being the 3C the most common. [9,10]. Another appealing feature of SiC is the possibility of fabricating multiple nanostructures from it; espe- cially silicon carbide nanowires (SiCNWs). These nanowires have been intensively investigated by many researchers due to their interesting properties, such as high mechanical strength, and the inherited properties from their bulk counterparts, such as chemical inertness and wide bandgap [11–13], enabling potential applications in electronics, optics, advanced engineering and nano- electromechanical switches [14–16]. 3C-SiC nanowires are particu- larly interesting from an application standpoint; for instance, Alper et al. [17], built a supercapacitor using SiCNWs as electrodes. It has been also suggested that they could be used to scale down the size of devices as well as enhancing the sensitivity of sensors [18]. It is worth mentioning that many theoretical works study 3C-SiCNWs, grown along the [1 1 1] direction, with hexagonal cross-sections, since they can be compared with the hexagonal polytypes and also due to their higher stability in comparison with other growth directions [19]. In this respect, Oliveira et al., predicts that the 2H polytype nanowires are more stable for diameters less than 20 nm [20], however, there is still controversy about the diameter in which the 3C-SiCNWs are stable [20], then a study of the properties of 3C-SiCNWs with other growth directions would be interesting in order to investigate if their synthesis is possible, hence [1 1 0] nanowires are particularly interesting since Si and https://doi.org/10.1016/j.commatsci.2017.10.021 0927-0256/Ó 2017 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail addresses: jcuevasf@gmail.com (J.L. Cuevas), alejandtb13@gmail.com (A. Trejo), amirandad.ipn@gmail.com (Á. Miranda), lperez@fisica.unam.mx (L.A. Pérez), irisson.ipn@gmail.com (M. Cruz-Irisson). Computational Materials Science 142 (2018) 268–276 Contents lists available at ScienceDirect Computational Materials Science journal homepage: www.elsevier.com/locate/commatsci