PhD Research Proposal
By Amjid Iqbal
Photo activated room temperature CO2 gas sensor fabrication using BaTiO3–CuO nano composite thin films
My Ph.D work will be based on the fabrication of photoactivated CO2 gas sensor operation at room temperature using BaTiO3–CuO thin film. In this research proposal, the applications and the demand for simple and low-cost miniaturized metal oxide semiconductor based CO2 sensors have been briefly described. There are certain problems associated with metal oxide semiconductor based gas sensors such as high-temperature operation, high power consumption, and stability which, make it unreliable in explosive and flammable environments. These problems can be resolved by using certain well-characterized nanocomposite materials and replacing the thermal energy operation of these sensors with photonic energy. In order to address these issue in recent technology, we propose BaTiO3–CuO nanocomposite thin films gas sensor operation at room temperature by illuminating it with an ultraviolet light source.
The carbon dioxide CO2 is one of the greenhouse gas that contributes to environmental pollution. With the aim to control the air pollution and to detect CO2 gas at low levels in the air, there is a growing need for compact and accurate CO2 gas sensors that can be efficiently deployed in large area sensor networks to monitor trends in greenhouse gas concentrations 1. The CO2 gas sensors have also potential applications in others fields, such as indoor air quality control, process control in fermentation, monitors for biotechnology and so on. The most common approach to detect CO2 is based infrared spectroscopy and gas chromatography 2. Unfortunately, these techniques are expensive, bulky and not well suited for online monitoring. Therefore, it is necessary to develop a simple and low-cost method for a miniaturized CO2 gas sensor of high performance.
Semiconductor metal oxide chemoresistive type gas sensors are alternative due to their ability to alter conductance with modest detection limits, small size, low cost and on-line monitoring 3-5. CO2 is very difficult to detect by conventional gas sensors due to its high stability at room temperature. So to ensure the rapid and reversible operation of such type of sensor, the operation temperature is typically maintained between 200 and 400OC 6. Up to now, many efforts have been made to study the functionality and performance of chemi-resistive sensors by using a wide variety of metal oxides in various compositions of different dopants, catalysts, adhesives, and binders 7. However, the major issues are still existed associated with the operating condition and stability. In such type of sensors, there is a need to integrate heating elements within sensor devices with power consumption as high as hundreds of mW, which remains a burden for portable devices operating with batteries. Apart from power consumption, a high-temperature operation of semiconductor chemical sensors based on thin or thick films composed of metal oxide results in long-term instability reflected in the drift of both sensor resistance and response 8. The low-temperature operation makes it reliable and safe in explosive and flammable environments while ensuring the long-term stability of the sensors by negligible diffusion and sintering effects in the materials.
Therefore the room temperature operation of the gas sensor is highly demanded which is a challenging issue. Photonic energy is the alternate approach to thermal energy which can promote the surface reaction on the surface of the metal oxide sensing layer without increasing the temperature of the sensor 9. The use of photonic energy generates electron/hole pairs which increase the density of charge carriers throughout the material and could decrease the intergrain barrier height by changing the intergrain state’s charges, leading to decrease the depletion layer widths in the adjacent grains 10-11. In order to address this issue in recent technology, we will use photo-activated composite semiconductor sensors operating at room temperature. We propose BaTiO3–CuO nanocomposite photoactivated as a carbon dioxide gas sensor. The properties of the proposed nanocomposite as a CO2 gas sensor thermally activated have been reported in thick and thin films forms 12-14. A different approach will be employed in my Ph.D to fabricate BaTiO3–CuO sensing layer structure. We will deposit first sensing layer on different substrates like ITO, sapphire and glass substrate by using suitable available physical vapor deposition (PVD) technique. The sensing layer will be analyzed by using different characterization techniques such as TEM, XRD, XPS and photoactivated IV. After optimization of sensing layer, nobel metal such as Pd, Ag, Au and Ag etc. of few nano meter thickness will be deposited on active layer to enhance the surface reaction.The complete device will be formed by by fabricating interdigitated patterns of platinum on active layer using photolithograhy and dry etching. Electrical characterization and photoactivation will be performed inside a sealed stainless steel chamber, where the target atmosphere will be obtained by means of mass flow controllers.
Collecting the literature and previous related work to the project assumption on “Photo activated room temperature CO2 gas sensor fabrication using BaTiO3–CuO nano composite thin films “. A literature review should help to give a context for the planned research. This can be divided into three areas: defining the topic, selecting relevant keywords, and setting limits to research. Read with a critical eye, were there any limitations to previous work, or any mistakes? What did the researchers conclude? Were there useful recommendations?
BaTiO3–CuO thin films preparation and optimization
?Sample preparation is the essential aim of the PhD work. Therefore, start will be taken to prepare BaTiO3–CuO thin films on different substrates using suitable availabe PVD thin films growth technique to ascertain the best method to obtain good quality films using the structure tools confirmations, TEM, SEM, XPS and the factors affecting the film homogeneity and photo activated I-V characteristics will be tested.
Optimization of metal additive
The next step will be the optimization of catalytic layer of the nobel metal such as Pd, Ag, Au and Ag etc. on active layer to enhance the surface reaction. Nobel metal of few nanometer thickness will be deposited on the active layer using sputtering technique.The films will again be characterized by using XRD, TEM, and XPS to find the crystal structure, size and shape.
After optimization of active thin layer the device will be formed by fabricating interdigitated patterns of platinum on active layer using photolithograhy and dry ethching. In this step the thickness and the spacing of the interdigitated pattern will be optimized.
?The gas sensing properties of the fabricated devices will be measured with out heating under specific ultra violet light illumination inside a sealed stainless steel chamber. The variation in sensor resistance will be monitored in test gas (CO2) enviroment using I-V source measurement unit. Gas flow will be controlled using mass flow controllers, and all measurements will be recorded to a computer through the use of LabVIEW over a GPIB interface. The current–voltage characteristics of the fabricated sensors will measure to check the contribution of the contact resistance between Platinum IDEs and BaTiO3–CuO sensing film to the overall performance.
?The proposed study will be conducted bearing in mind issues of costs, time and availability of the deposition and characterization techniques. It will be carried out in four phases.
Phase-I will involve an in-depth literature review to achieve a more detailed of
Gas sensing materials framework. Along with learning of the different deposition and characterization techniques.
During phase-II, experimental work will be carried out for test cases and then for the
Gas sensing applications.
During phase-III, the data collected will be analyzed and interpreted to come out with
the research findings. If required more experiments will be done at this stage.
Thesis work and paper writing will be completed during phase-IV.
Provisional Time line
Phase -I will be completed in first six months at the start of PhD period.
Phase -II will take about one year.
Phase -III might take one year.
Thesis and paper writing will be completed in about six month period.
REFRENCES AND LIST OF PUBLICATIONS
M. Guangcan, C. Horvath, M. Aktary, and V. Van”Silicon microring refractometric sensor for atmospheric CO2 gas monitoring”OPTICS EXPRESS 1773, Vol. 24(2), 2016. DOI:10.1364/OE.24.001773
Ch. Ju. Chiang, K.T. Tsai, Yi.H. Lee, Hu.W. Lin, Yi. L. Yang,and Ch. C. Shih etl” In situ fabrication of conducting polymer composite filmas achemical resistive CO2 gas sensor” Microelectron. Eng. 111 (2013) 409–415.
J. H. Lee “Gas sensors using hierarchical and hollow oxide nanostructures:Overview”. Sens. Actuators B 140 (2009) 3192336 .
J. Herr an et al., “Photoactivated solid-state gas sensor for carbon dioxide detection at room temperature” Sens. Actuat. B Chem. 149 (2010) 368–372.
E. Comini,. et al. “Quasi-one dimensional metal oxide semiconductors: Preparation, characterization and application as chemical sensors” Prog. Mater.Sci. 54 (2009) 1267.
G. Eranna, B. C. Joshi, D. P. Runthala, ; R. P. Gupta “Oxide materials for development of integrated gas sensors – A comprehensive review” Crit. Rev. Solid State Mater. Sci. 29, 1112188 (2004).
N. Yamazoe, G. Sakai, and K. Shimanoe “Oxide semi conductor gas sensors” Catal. Surv. from Asia 7 (2003) 63–75.
G. Chen, G. Paronyan, T. M. Pigos, ; A. R. Harutyunyan “Enhanced gas sensing in pristine carbon nanotubes under continuous ultraviolet light illumination” Sci Rep 2, 343 (2012).
J. D. Prades,. et al. “Equivalence between thermal and room temperature UV light-modulated responses of gas sensors based on individual SnO2 nanowires” Sens. Actuators B. 140 (2009) 337–341.
H. Chen et al., “A comparative study on UV light activated porous TiO2 and ZnO ?lm sensors for gas sensing at room temperature” Ceram. Int. 38, 503–509 (2012).
E. Comini, A. Cristalli, G. Faglia, and G. Sberveglieri “Light enhanced gas sensing properties of indium oxide and tin dioxide sensors” Sens. Actuat. B Chem. 65 (2000) 260–263.
J. Herrán, et al., “On the structural characterization of BaTiO3–CuO as CO2 sensing material” Sens. Actuators B 133 (2008) 315–320.
Q. Wei, W.D. Luo, B. Liao, Y. Liu, G. Wang “Giant capacitance effect and physical and physical model of nano crystalline CuO–BaTiO3 semiconductor as a CO2 gas sensor” J. Appl. Phys. 88 (2000) 4818–4824.
G. Ga Mandayo, F. González, I. Rivas, I. Ayerdi, J. Herrán “BaTiO3–CuO sputtered
thin-film for carbon dioxide detection” Sens. Actuators B 118 (2006) 305–310.
Amjid Iqbal*, Arshad Mahmood, Q. Raza, A.Shah, Rashad Rashid, Zahid ali and A. Malik”Photo luminescence and structural analysis of wurtzite (ZnO)1-x(V2O5)x composite” Journal of Semiconductors (IOP), Accepted.
Arshad Mahmood, Amjid Iqbal and Q. Raza”Effect of Thermal annealing on the structural, morphological and optical properties of V2O5 thin fims”Journal of luminescence (Elsevier),submitted.
Faisal Aftab, Javaid Iqbal, Amjid Iqbal, Arshid Mahmood and Qaiser Raza “Effect of Cu incorporation on the physical properties of CdS thin films deposited by Thermal evaporation technique “Journal of the Koreon Physical Society, Volume 69, Issue 4, pp 593-597.
Ijaz Ali, Amjid Iqbal, Arshad Mahmood, A. Shah, M. Zakria and Asad Ali “Optical analysis of Annealed Cd1?xZnxSe thin films deposited by close space sublimation technique” Materials Science-Poland, 34(4), 2016, pp. 828-833.
Hafeezullah, Amjid Iqbal, M.zakria, Arshad Mehmood “Structural and Spectroscopic analysis ofwurtzite (ZnO)1-x(Sb2O3)x composite” Progress in Natural Science: Materials International Volume 25, Issue 2, April 2015, Pages 131–136.
Taj Muhammad Khan, Amjid Iqbal, M. Zakria”Study of excitonic UV emission stability,green luminescence and band gap tunibility in wurtzite (ZnO)1-x(Cr2O3) composite” Vacuum, Volume 105, July 2014, Pages 1-6. Citation 26
Qeemat Gul, M. Zakria, Taj Muhammad Khan, Arshad Mahmood, Amjid iqbal “Effect of Cu Incorporation on physical properties of ZnTe thin films deposited by Thermal evaporation”Materials Science in Semiconductor Processing, Volume 19, March2014, Pages 17-23.
Amjid Iqbal, Taj Muhammad Khan, A. Mahmood”Structural and optical properties of Cr doped ZnO crystalline thin ?lms deposited by reactive electron beam evaporation technique” Progress in Natural Science: Materials International 2013;23(1):64–9.Citation 26
M. Arslan, A. Maqsood, A. Mahmood, Amjid Iqbal “Structural and optical properties copper enriched ZnSe thin films prepared by closed space sublimation technique” Materials Science in Semiconductor Processing 16 (2013) 1797–1803.Citation 6.
T. M. Khan, M. F. Mehmood, Arshad Mahmood, A. Shah, Q. Raza, Amjid Iqbal, U. Aziz “Synthesis of thermally evaporated ZnSe thin film at Room Temperature” Thin Solid film Volume 519, Issue 18, 1 July 2011, Pages 5971–5977.Citation 41.