Figure 1. Structure and electron emission performances of a GME.

(a) A schematic drawing showing the structure of a GME and its working principle. A GME is fabricated on a SiO₂/Si wafer substrate and consists of a graphene film suspended between two metal (Au/Cr) electrodes and over the bottom Si electrode. A bias voltage (V_b) is applied to a GME to drive the electron emission from it and a top W electrode with a collecting voltage (V_c) applied is used to collect and measure the emission current. The highly doped Si layer applied with a voltage of V_g acts as the gate to tune the emission current measured by the top W electrode. (b) Tilted SEM image of a GME (scale bar, 1 μm). (c) Raman spectrum of a GME exhibiting a G peak of 1,580 cm⁻¹ and a 2D peak of 2,656 cm⁻¹. (d) Emission current of a GME measured by the upper collector electrode (I_c, solid blue line) and the bottom gate electrode (I_g, solid olive line) and the corresponding applied Joule-heating power (dashed purple line) when ramping up V_b and fixing V_c (100 V) and V_g (15 V). (e) I_c−V_g curves of the same GME as in c when V_b increases from 3.10 to 3.35 V at 0.05 V intervals and V_c is fixed at 100 V.