# Configurational Effects on Strain and Doping at Graphene-Silver Nanowire Interfaces
## 2 Results and Discussion
As shown in Figure 3d, the flat graphene exhibits a tensile strength of 0.01%, while the graphene-covered AgNW region depicts a strain generation of 0.06%, implying a tension increase  
Figure 3: Raman spectroscopy of Gr/AgNW heterostructure (**a**) typical Raman spectrum of graphene-covered AgNW and graphene only region. Slight effect of surface-enhanced Raman scattering (SERS) and redshifts of G and 2D peak are observed in Gr/AgNW heterostructure. (**b**) Raman line map (indicated by the purple line) across the AgNW along the axial direction and (**c**) transverse direction. In both cases, the G and 2D peak intensity increases at the Gr/AgNW region (red colour in background), compared to the Gr/ITO region (blue colour in background). Redshifts of both peaks are also recognised at the AgNW region. (**d**) Strain and doping map of the above regions shows tensile strain of approximately 0.06% at the graphene-covered AgNW compared to graphene only region. Electron concentration is comparable within two regions. by 5 folds due to the embedded AgNW. This result shows that the conforming of graphene on the curvature of AgNW induces strain. Similar morphology studies are performed in the different stacking arrangement of AgNW/Gr. We observed comparable height of graphene in covered and uncovered AgNW (Figure 4b,c), which indicates graphene attachment on AgNW does not lead to significant alternation in topography. Nevertheless, uncovered AgNW influences the adhesion force map and results in a drop in adhesion force of 30 nN due to different hetero interactions between uncovered AgNW and the tip apex. The surface potential analysis in Figure 4c,d demonstrates a reduction of \(\varphi\) of 0.2 eV across the AgNW region compared to the graphene substrate, which is in consonance with the Gr/AgNW system. In both stacking arrangements of graphene and AgNW, the local p-n-p junction has been observed. Figure 4: AFM and KPFM mapping of AgNW/Gr heterostructrue: (**a**) AFM topography and (**b**) adhesion force map of AgNW network above monolayer graphene. A reduction in adhesion is observed. (**c**) Morphology and (**d**) work function of AgNW/Gr system indicate a drop in 0.2 eV across the AgNW region. The effect on the strain and spatial charge distribution in AgNW/Gr heterostructure is also studied by Raman spectroscopy, where AgNW region displays SERS effect and redshifts in both G and 2D peaks compared to that of the bare graphene (Figure 5a), similar to the Gr/AgNW system. Line maps across the AgNW along the axial direction (Figure 5b) and the transverse direction (Figure 5c) conveys an increase of G and 2D peak intensity up to 800% and 200% in the AgNW region, revealing a more notable SERS effect than the Gr/AgNW heterostructure. In addition to the 2.7% light absorbance of graphene, which should play minimal role, we suspect this phenomenon is due to curvature-induced strong interaction between graphene and AgNW, which leads to reduction of hot spots for SERS to take place in Gr/AgNW system [14; 25]. It is also noteworthy that additional peak at around 1520 cm\({}^{-1}\) is observed in AgNW/Gr spectrum, which arises from the PVP coating residue around AgNW [26]. The topping of AgNW induces redshift of G\(\omega\) and 2D\(\omega\) by 3 cm\({}^{-1}\) and 5 cm\({}^{-1}\), respectively, compared to the flat graphene, which is, upon constructing a correlation plot with parallel strain and doping axes in Figure 5d, responsible for a tensile strain of 0.01% induced by the nanowires. It clearly shows that AgNW lying on top does not induce any profound change in tensile strain in graphene but a slight extension of carbon-carbon bonds as compared to graphene over ITO surface. In both AgNW/Gr and Gr/AgNW system, the Raman analysis shows dominant response from strain than doping.