# Configurational Effects on Strain and Doping at Graphene-Silver Nanowire Interfaces
## 1 Introduction  
Graphene has always been a promising material for sensors, supercapacitors, and optoelectronics application by virtue of its high electrical conductivity, optical transmittance, and large surface area [1; 2]. In recent years, the incorporation of silver nanowires (AgNWs) into graphene has compelled substantial attention due to the presence of surface plasmon resonance (SPR), which boosts the performance of photovoltaic devices [3], as well as the conductivity enhancement in the graphene-based transparent electrode [4]. Graphene can also act as a protective layer to AgNW with minimal disruption to the light transmittance [5]. While the benefit appears to be considerable, one should also inspect the physical and chemical influences, be it advantageous or disadvantageous, due to the addition of AgNW.  
The hybrid system of graphene and AgNW can be regarded as textured surface and differentiated into two stacking arrangements: 1) graphene (Gr)/ silver nanowire (AgNW), where graphene covers the individual nanowire and induces strain at the curvature; and 2) AgNW/Gr, where the nanowire lies on the top of the graphene sheet, which generates less strain but some extension of carbon-carbon bond. Literature reveals the induced strain enhances electron-phonon coupling and potentially turns graphene into a Bardeen-Cooper-Schrieffer (BCS) superconductor [6]. Uniform uniaxial strain may also tune the electronic structure of graphene by shifting the Dirac cone and Landau quantization, which is crucial to explore the new field \"straintronics\" where strain is engineered to achieve innovative applications [7; 8]. Considering the work function difference between graphene and AgNW, electron (hole) will in general transfer from lower (higher) work function material to higher (lower) work function material [9]. This n-type (p-type) doping creates a p-n junction, which possesses peculiarproperties such as quantum interference and Klein tunnelling [10; 11]. Hence, understanding the strain and doping of graphene induced by the sandwiching of AgNW is indispensable.  
The strain and doping configuration of graphene with the incorporation of silver nanostructure has been broadly studied in Raman spectroscopy, yet the conclusions are conflicting. [PERSON] et al. [12] recorded stiffening of G mode and 2D mode due to embedding of silver nanoplates and suggested p-doping in graphene, while [PERSON] and coworkers [13] observed upshift of G mode but downshift of 2D mode in graphene-covered silver nanoparticles (Gr/AgNPs) and claimed n-doping. Similar disagreement in doping direction can also be found in silver nanoparticles-stacked graphene (AgNPs/Gr) [3; 14], and whether tensile or compressive strain is induced by the sandwiched AgNPs is still under dispute [3; 13; 14]. This contradiction arises mainly from the lack of a universal decoupling methodology of strain and doping from the Raman modes. The graphene heterostructure with AgNW, another family member in silver nanostructure, is rarely investigated; it is therefore essential to develop a comprehensive approach to study the strain and doping in Gr-AgNW system.  
In the present work, we prepared two hybrid systems of single layer graphene and AgNW in different stacking orders, Gr/AgNW and AgNW/Gr, to investigate the graphene-silver interaction in different configurations. In both stacking arrangements, a similar magnitude of drop in work function in graphene has been observed by Kelvin probe force microscopy (KPFM). It leads to generation of lateral p-n-p junction as Gr/indium tin oxide (ITO)-Gr/AgNW/ITO-Gr/ITO. Subsequently, we demonstrated decoupling of strain and doping in our hybrid structure from the method developed by [PERSON] et al. [15], and recognised that AgNWs (\(\approx\) 20 nm in height) exert more influence on tensile strain than charge transfer in both stacking order.