Optimization of multilayer graphene-based gas sensors by ultraviolet photoactivation

Nitrogen dioxide (NO₂) is a potential hazard to human health at low concentrations, below one part per million (ppm). NO₂ can be monitored using gas sensors based on multi-layered graphene operating at ambient temperature. However, reliable detection of concentrations on the order of parts per million and lower is...

Investigation of multi-layered graphene/silicon Schottky junction in oxidizing atmosphere

In this study, we investigate a Schottky junction based on solution-processed multilayered graphene (MLG). We present a rectifying device obtained with a straightforward approach, that is drop-casting a few microliters of MLG solution simultaneously onto Si, Si-SiO2 and Si-SiO2-Cr/Au surface. Monitoring the modulation of Schottky barrier...

Influence of defect density on the gas sensing properties of multi-layered graphene grown by chemical vapor deposition

Chemical vapor deposition (CVD) has been demonstrated as a highly promising technique for the production of graphene on large scale and enabling tunability of the intrinsic defects of the films during the synthesis.<br/><br/>In this work, we report on the correlation between the density of defects (DoD) and the kinetics of interaction of multi...

Functionalisation of Multi-Layer Graphene-Based Gas Sensor by Au Nanoparticles

A novel gas sensor based on multi-layered graphene (MLG) functionalised with gold nanoparticles (Au-NPs) is presented. We demonstrate for the first time that: (1) the signal saturates during the analyte exposure, something which does not occur in the pristine material and in graphene-based gas sensors in general; (2) the sign of the device...

Low-humidity sensing properties of multi-layered graphene grown by chemical vapor deposition

Humidity sensing is fundamental in some applications, as humidity can be a strong interferent in the detection of analytes under environmental conditions. Ideally, materials sensitive or insensitive towards humidity are strongly needed for the sensors used in the first or second case, respectively. We present here the sensing properties of...

Wafer-scale transfer-free process of multi-layered graphene grown by chemical vapor deposition

Chemical vapour deposition (CVD) has emerged as the dominant technique to combine high quality with large scale production of graphene. The key challenge for CVD graphene remains the transfer of the film from the growth substrate to the target substrate while preserving the quality of the material. Avoiding the transfer process of single or...

Growth of multi-layered graphene on molybdenum catalyst by solid phase reaction with amorphous carbon

A method to grow multi layers graphene (MLG) just by thermal annealing in an inert atmosphere is reported. A molybdenum (Mo) catalyst layer is used in combination with a solid amorphous carbon (a-C) source on top or below the Mo layer. The formation of MLG directly on top of the catalyst substrate surface is confirmed by Raman spectroscopy,...

Analysis of a calibration method for non-stationary CVD multi-layered graphene-based gas sensors

Limitations such as lack of detected stationary signal and slow signal recovery after detection currently affect graphene-based chemi-sensors operating at room temperature. In this work, we model the behavior of a sensor in a test chamber having limited volume and simulating the environmental conditions. From this model, we mathematically derive...

A transfer-free approach to wafer-scale graphene deposited by chemical vapour deposition

Effects of graphene defects on gas sensing properties towards NO 2 detection

The crystal structure of graphene flakes is expected to significantly affect their sensing properties. Here we report an experimental investigation on the crystalline structure of graphene aimed at exploring the effects on the gas sensing properties. The morphology of graphene, prepared via Chemical Vapor Deposition (CVD), Liquid Phase...

Low Temperature CVD Grown Graphene for Highly Selective Gas Sensors Working under Ambient Conditions

In this paper we report on gas sensors based on graphene grown by Chemical Vapor Deposition at 850 °C. Mo was used as catalyst for graphene nucleation. Resistors were directly designed on pre-patterned Mo using the transfer-free process we recently developed, thus avoiding films damage during the transfer to the target substrate. Devices...

High sensitive CVD graphene-based gas sensors operating under environmental conditions

An innovative approach to overcome saturation and recovery issues of CVD graphene-based gas sensors

<br/>In this work, we present an innovative method which enables to solve fundamental limitations affecting graphene-based chemi-sensors operating under environmental conditions, namely the lack of signal saturation and the scarce recovery after the detection step. The method, which exploits the differential current instead of the current itself...

High sensitive gas sensors realized by a transfer-free process of CVD graphene

The work herein presented investigates the behavior of graphene-based gas sensors realized by using an innovative way to prepare graphene. The sensing layer was directly grown by chemical vapor deposition on pre-patterned CMOS compatible Mo catalyst and then it was eased on the underlying SiO2 through a completely transfer-free process. Devices...

A transfer-free wafer-scale CVD graphene fabrication process for MEMS/NEMS sensors

In this paper we report a novel transfer-free graphene fabrication process, which does not damage the graphene layer. Uniform graphene layers on 4" silicon wafers were deposited by chemical vapor deposition using the CMOS compatible Mo catalyst. Removal of the Mo layer after graphene deposition results in a transfer-free and controlled placement...