In this paper, a miniature graphene-based field emission pressure sensor is reported for the first time, in which carbon nanotubes have been applied as the cathode and reduced graphene oxide sheets have been utilized as the flexible anode. Since, graphene is the thinnest (one atom thick) known structure with a uniform thickness, graphene based membrane is a promising candidate for pressure sensors which allows both high sensitivity and very small chip area, simultaneously. A maximum sensitivity of about 21.9μA/A/Pa is achieved at the bias voltage of 5 V for the fabricated field emission pressure sensor, which is about two orders of magnitude higher than the previously reported graphene based pressure sensors. The fabricated structure has been also used as a graphene based resonator in which emission current is applied to detect the mechanical resonance, efficiently. The measured resonance frequency is measured about 10 MHz, which is shifted to lower frequencies by increasing the ambient pressure. The measured sensitivity, for the resonant operation mode, is about 11.32 Hz/Pa (S = Δf/ΔP). Owing to the inherent low mass of graphene, the presented structure can be entitled as a promising resonant pressure sensor.

The formation of high sensitivity-wide dynamic range field emission pressure sensors based on carbon nanotubes (CNTs) is reported. In this work, CNTs are grown inside an array of micromachined holes in order to ensure a high sensitivity and a wide dynamic range by allowing anode-cathode proximity while preventing anode-cathode direct contact simultaneously. External pressure is applied to a Si-based flexible anode, which results in consequent variations in emission current, due to electric field changes. Microcavities in this structure have been formed by a Si deep vertical etching process, while the CNTs have been grown by direct current plasma-enhanced chemical vapour deposition. Also, it is demonstrated that a similar fabrication process can be applied to implement a device with an electrically controllable emission current. A high sensitivity of 1.5-13.7 μA kPa^-1 (with V_{anode/cathode} < 100 V) within a dynamic range from around 0.1 to 1 GPa, is measured in this experiment.