Research On Photomechanical Uncooled Infrared Focal Plane Based On Super-aligned Carbon Nanotubes

Infrared thermal imaging technology,one of the most crucial methods of target detection and recognition,has found an increasingly wide utilization in military and civil fields.For optomechanical uncooled infrared focal plane array(FPA),infrared radiation detection and subsequent reconstruction of an image are achieved by optically acquiring the deflection of individual bi-material microcantilevers without readout integrated circuit(ROIC).In order to improve the temperature sensitivity and response time of FPA,research of optomechanical uncooled infrared focal plane array based on Super-aligned carbon nanotubes(CNT)is carried out herein.The theoretical results indicat that the temperature sensitivity of FPA is increased by 1.3 times and the response time is reduced by half due to the application of CNT.The main contents of this dissertation are as follows:Firstly,in order to utilize the axial properties of CNT and solve the compatibility with MEMS manufacturing process,the vertically aligned CNT forests are self-assembly transformed into a closely packed,highly aligned horizontal CNT film by liquid capillary force.In the investigations of the mechanical properties and thermal response of the CNT film,it is indicate that the sliding between the tubes limits not only the strength,but also the thermal sensitivity of the bi-material microcantilevers.Inter-tube deposition of Al3O2 thin films by ALD is used to reinforce the binding between the tubes,and increases in both the mechanical strength and thermomechanical response of the CNT microcantilevers have been achieved.Secondly,the microcantilever pixel of the photomechanical FPA based on carbon nanotube is designed in detail,including materials selection,infrared optics,thermal model,thermomechanical response,time constant,and pixels array layout.According to the designed FPA structure,the related microfabrication process is explored.The exploration of key processes is described in detail,including CNT-related processe,bi-material cantilever forming processe and sacrificial layer removal processe,and an intergrated microfabrication process of FPA developed.Finally,an optical readout system of photomechanical infrared thermal imaging is built,which consists of an optical module,a temperature control module and a vacuum module.Combined with the designed FPA structure and optical readout system,the inherent noise limited by FPA itself and the noise limited by the system as well as the noise equivalent temperature difference(NETD)are analyzed.The response of the pixel to the infrared source is measured by the optical readout system.