Characterization of a new sensing device based on hydrocarbon groups (CHx) coated porous silicon (original) (raw)

CHx - porous silicon structures for gas sensing applications

physica status solidi (c), 2005

We have developed a gas sensor for hydrocarbons using layered structures hydrocarbons /porous silicon. Sensitivity of this device, response time and capacitance response to different gases (ethane, ethylene and propane) have been studied. DC and AC electrical measurements were performed to test the sensor and it has been shown that CH x layer-PS/p-Si structure is modified by the gas reactivity on the PS/CHx surface. Finally, FTIR spectroscopy measurements in different gas environments have shown remarkable change of chemical composition of the sensor material as a result of its interaction with gases.

Analysis of Porous Silicon Devices for Gas Sensors

2001

In this work the results obtained to develop gas sensor built with porous silicon (PS) are presented, showing the influence of organic vapors such as acetone and ethanol on electrical characteristics of devices made of Al/PS/Si/Al. The sensitivity of the PS was characterized observing changes in capacitance as a function of frequency by means of devices geometrically scaled according to perimeter/area ratio. The relationship between each organic substance and the variation of impedance with frequency was obtained, verifying that the performance of devices is not shifted by the test conditions. The behavior of complex impedance is typical of a disordered material. Also, through FTIR measurements, there is no evidence of change of PS structure due to a direct adsorption of gases, showing that the passivation of PS devices is effective to block the action of chemical substances in interface states.

Effect of current density on the porous silicon preparation as gas sensors**

Journal of the Mechanical Behavior of Materials

In this study, porous silicon (PSi) was used to manufacture gas sensors for acetone and ethanol. Samples of PSi were successfully prepared by photoelectrochemical etching and applied as an acetone and ethanol gas sensor at room temperature at various current densities J= 12, 24 and 30 mA/cm2 with an etching time of 10 min and hydrofluoric acid concentration of 40%. Well-ordered n-type PSi (100) was carefully studied for its chemical composition, surface structure and bond configuration of the surface via X-ray diffraction, atomic force microscopy, Fourier transform infrared spectroscopy and photoluminescence tests. Results showed that the best sensitivity of PSi was to acetone gas than to ethanol under the same conditions at an etching current density of 30 mA/cm2, reaching about 2.413 at a concentration of 500 parts per million. The PSi layers served as low-cost and high-quality acetone gas sensors. Thus, PSi can be used to replace expensive materials used in gas sensors that funct...

Porous Silicon Gas Sensors: The Role of the Layer Thickness and the Silicon Conductivity

Sensors

We studied the influences of the thickness of the porous silicon layer and the conductivity type on the porous silicon sensors response when exposed to ethanol vapor. The response was determined at room temperature (27 ∘C) in darkness using a horizontal aluminum electrode pattern. The results indicated that the intensity of the response can be directly or inversely proportional to the thickness of the porous layer depending on the conductivity type of the semiconductor material. The response of the porous sensors was similar to the metal oxide sensors. The results can be used to appropriately select the conductivity of semiconductor materials and the thickness of the porous layer for the target gas.

CO2 and H2 detection with a CHx/porous silicon-based sensor

Vacuum, 2006

There has been great interest in the last years in gas sensors based on porous silicon (PS). Recently, a gas sensing device based on a hydrocarbon CH x /porous silicon structure has been fabricated. The porous samples were coated with hydrocarbon groups deposited in a methane argon plasma. We have experimentally demonstrated that the structure can be used for detecting a low concentration of ethylene, ethane and propane gases [Gabouze N, Belhousse S, Cheraga H. Phy State Solidi (C), in press].

Observation of oxygen gas effect on porous silicon-based sensors

Thin Solid Films, 2006

In addition to its exciting electrooptical properties, porous silicon exhibits characteristics of interest for sensor devices. In this work, we report on a study of porous silicon layers for gas sensor applications. We describe our test system for gas sensors and investigate electrical behaviour of porous silicon layers (p-type) in oxygen gas for various fabrication conditions. The sensing mechanism is based on a gas-induced modulation of conductivity due to adsorbed molecules in the porous film. Results show that the current increases significantly as oxygen gas is adsorbed. Electrical conduction mechanisms of the sensors in ambient pressure and room temperature are proposed. The fabrication process could be easily integrated to large scale integrated technologies. The observed behaviour suggests that the application of porous silicon in future chemical gas and biological sensors is feasible.

EFFECTS OF THE POROUS SILICON MORPHOLOGY ON THE GAS SENSOR PERFORMANCE

In this work,porous silicon (PSi) based gas sensor of structure (AL/nPSi/n-Si/AL) at different morphologies was prepared on the n-type silicon substrate using IR illuminated source of wavelength (810nm). The morphological and gas sensing properties of the sample were studied, under various etching time (5-20min). The current density –voltage characteristic at temperaturefrom 25 to 150 °C of the sensor,which was sensitivity analysis based on the silicon nano size, porosity, layer thickness, and effective dielectric constant of the PSi layer.The SEM image of the PSi layer showed the formation single layer structure pore –like the cylindrical and rectangular pore shape. The porous layer after etching time (5-10min) and double of mud _like for 20min produced different dimensions with randomly distributed as an upper layer and pore _like structure as a lower layer. The current density–voltage analysis confirms that higher temperatures with the presence of CO2 gas lead to sharply increase the sensitivity with the current and voltage. Overall, the improvement that appeared on the double porous layer sensitivity due to the higher value of the surface area.

Gas sensitive porous silicon devices: responses to organic vapors

Sensors and Actuators B: Chemical, 2003

Geometrically scaled PS-based structures were fabricated in order to develop gas sensing devices by exploring porous silicon (PS) electrical characteristics. The electrical behavior of PS devices respond to polar organic vapors (as acetone and ethanol) reversibly in a reproducible way.

Gas sensors based on silicon devices with a porous layer

physica status solidi (c), 2005

In this work two silicon devices, that is a FET and a p crystalline silicon resistor having porous silicon as adsorbing layer are presented as gas sensors. Owing to they are easily integrable with silicon electronics, these devices could represent an improvement of the functionality of silicon for sensor applications. Unlike other porous silicon-based sensors, in this case the sensing variable is a current flowing in the crystalline silicon, so that the porous silicon film has only the function of adsorbing layer and its properties, electrical or optical, are not directly involved in the measurement. The fabrication processes and an electrical characterization in presence of isopropanol vapors are presented and discussed for both devices.

Gas Sensing Properties of Porous Silicon

Analytical Chemistry, 1995

Conductivity of porous silicon layers (ptype) has been investigated for oxganic vapor sensing. A many orders of magnitude increase in conductivity in response to a vapor pressure change from 0 to 100% has been measured for some compounds. The conductivity (at a constant pressure) varies exponentially with the compound's dipole moment. The temporal response of the porous silicon layers is in the seconds range, and the recovery is much slower (minutes). However, due to the tremendous conductivity changes and the low background noise, a complete recovery is not needed for sensing purposes. The mechanism of conductivity enhancement has been studied us@ several methods. It is attributed to an increase in the density of charge carriers. An additional mechanism based on increased diffusMty may take place in microporous silicon. The observed characteristics suggest the application of porous silicon to future chemical sensors. The sensors have the potential to be integrated monolithidly with other silicon devices using current technologies. Porous silicon CpS) is becoming an increasingly important electronic material in current fabrication technology. It has been suggested as a potential optical material for new silicon light emitting The fabrication of this material is carried out by a very simple electrochemical etching of silicon, which creates a network of nanometer-sized Si structures. Extensive studies have already been carried out on the electro-and photoluminescence properties of this material. Several models have been proposed to explain the origin of light emission, including quantum codnement effects,1s2J0J radiative recombination via (1) Canham, L. T.