▎ 摘　　要

Graphene nanoribbons (GNRs) slanted on aggregate TiO2 nanotube arrays (A-TNTs) with various compositions as field-emitters are reported. The morphology, crystalline structure, and composition of the as-obtained specimens were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Raman spectrometry. The dependence of the turn-on electric field and the field enhancement factor beta on substrate morphology was studied. An increase of GNRs reduces the specimens' turn-on electric field to 2.8 V/mu m and the field enhancement factor increased rapidly to about 1964 with the addition of GNRs. Results show a strong dependence of the field emission on GNR composition aligned with the gradient on the top of the A-TNT substrate. Enhanced FE properties of the modified TNTs can be mainly attributed to their improved electrical properties and rougher surface morphology. (C) 2016 Elsevier Ltd. All rights reserved.