Hydrogen-Terminated Diamond Surface as a Gas Sensor: A Comparative Study of Its Sensitivities

Abstract

A nanocrystalline diamond (NCD) layer is used as an active (sensing) part of a conductivity gas sensor. The properties of the sensor with an NCD with H-termination (response and time characteristic of resistance change) are measured by the same equipment with a similar setup and compared with commercial sensors, a conductivity sensor with a metal oxide (MOX) active material (resistance change), and an infrared pyroelectric sensor (output voltage change) in this study. The deposited layer structure is characterized and analyzed by Scanning Electron Microscopy (SEM) and Raman spectroscopy. Electrical properties (resistance change for conductivity sensors and output voltage change for the IR pyroelectric sensor) are examined for two types of gases, oxidizing (NO2) and reducing (NH3). The parameters of the tested sensors are compared and critically evaluated. Subsequently, differences in the gas sensing principles of these conductivity sensors, namely H-terminated NCD and SnO2, are described.

The Undoped Polycrystalline Diamond Film—Electrical Transport Properties

“…Due to the rare feature of the negative value of electrons affinity of polycrystalline diamond layers, they seem to be one of the best such materials [ 6 ]. As the interaction between gas molecules and the diamond hydrogen-terminated surface should lead to the change of layer’s resistance [ 7 ]. To use diamond layers to realize reliable electronic devices, several problems are still to be solved.…”

Improved Gas Sensing Capabilities of MoS2/Diamond Heterostructures at Room Temperature

“…On the other hand, H-NCD reveals unique properties of P-type induced subsurface conductivity, also known as 2DHG, which is sensitive to exposed gas or organic molecules. , The change in resistance of H-NCD is caused by chemical reactions forming counterions on its surface via the electron transfer model . The gas interaction model with the widely established H-NCD subsurface doping mechanism is described in ref . The water molecule from the air humidity dissociates the ions H 3 O + and OH – .…”

“…The two remaining electrons from the chemical reaction are released back into the conduction band of MoS 2 or form new O 2 − ions with O 2 . 2,4,6,22,40 On the other hand, the reducing gas NH 3 (Figure 5b) reacts with chemisorbed O 2 − ions and creates H 2 O and N 2 . 5 The remaining electron from the reaction is released into MoS 2 and reduces the resistivity of the sensing layer.…”

“…3,20 During the recovery process, i.e., after the change of the reducing gas to synthetic air, O 2 is chemisorbed from the atmosphere onto the surface of MoS 2 . 5,6,14,20,40 On the other hand, H-NCD reveals unique properties of Ptype induced subsurface conductivity, also known as 2DHG, which is sensitive to exposed gas or organic molecules. 25,26 The change in resistance of H-NCD is caused by chemical reactions forming counterions on its surface via the electron transfer model.…”

“…24,26 The MoS 2 /SiO 2 /Si sample is characterized by a Si peak at 520 cm −1 and two narrow peaks at 381 and 406 cm −1 attributed to MoS 2 . 7,40 The Raman spectrum of MoS 2 /H-NCD/ SiO 2 /Si combines all the peaks described above.…”