Dielectric loss and related noise of pyroelectric modi®ed lead titanate arrays V.N. Leonov a , D.P. Butler a ,Z.C ß elik-Butler a, * , K.R. Udayakumar b , C.M. Hanson b , H.R. Beratan b a School of Engineering and Applied Sciences, Southern Methodist University, P.O. Box 750338, Dallas, TX 75275-0338, USA b Raytheon Electronic Systems, Raytheon Infrared Center of Excellence, P.O. Box 660246, MS-37, Dallas, TX 75266, USA Received 10 May 2000; received in revised form 18 January 2001 Abstract Electrical characteristics of pyroelectric modi®ed lead titanate arrays were measured at dierent temperatures. The modi®ed lead titanate ®lms were deposited by metal-organic decomposition. Dielectric loss tangent tan d)aslowas 0.045 at 30 Hz was obtained at room temperature with lanthanum nickel oxide electrodes. For the purpose of this study,micromachined40 40 lm 2 pixelsmadeof200-nm-thickpyroelectric®lmswereconnectedinparallelinto10-or 100-pixel arrays. Noise measurements showed the temperature and frequency dependence of tan d noise to coincide with the calculated results. At room temperature, the best 10-pixel array showed a tan d noise current as low as 2 10 15 A/Hz 1=2 attheoperatingframerateof30Hz.Asexpected,1=f noise was observed proportional to applied current when the pixels were dc biased. Ó 2001 Published by Elsevier Science Ltd. Keywords: Dielectric loss; Noise; Tan d noise; Pyroelectric; Uncooled; Infrared; Focal plane array; Thermal imaging 1. Introduction The new generation of uncooled focal plane arrays caused revolutionary changes in both commercial and defense applications of uncooled infrared IR) imaging. ThenoiseequivalenttemperaturedierenceNETD)isa generally accepted measure of sensitivity for these IR imagers[1].Recently,NETDaslowas14mKhasbeen demonstrated by Raytheon Systems Company [2], and further improvements are expected down to the theo- retical limit of background limited NETD [3]. The current production of military and commercial IR imaging systems at Raytheon is based on hybrid ferroelectric technology [4]. These systems are built around240 320imagingarrayswithpixelson48.5-lm centersandshowNETDaslowas38mK[5].However, current technology has some limitations on further im- provement. Recently, monolithic ferroelectric technol- ogy has been successfully demonstrated as a viable alternative to hybrid technology [6]. Such technology oersapotentialforNETDaslowasabout1mK,i.e., signi®cantly better than about 20 mK, the potential to achieve with hybrid technology [7]. One of the promising candidates as a pyroelectric detector material for such a technology is modi®ed lead titanate thin ®lms deposited by metal-organic decom- position.Thisinvestigationisdevotedtoimpedanceand dielectric loss noise measurements on arrays of 240 320 self-supporting micromachined capacitor structures pixels) with modi®ed lead titanate as the IR sensitive pyroelectric ®lm and lanthanum nickel oxide electrodes. Arrays were formed by gangs of 10 and 100 pixels connected together in parallel. The investigation consists of two parts: the ®rst is tan d measurements; and the second one is related to bothcalculationof tan d noiseusingmeasured tan d and direct noise measurements on the pyroelectric detectors. Solid-State Electronics 45 2001) 735±741 * Corresponding author. Tel.: +1-214-768-3324; fax: +1-214- 768-3573. E-mail address: zcb@seas.smu.edu Z. C ß elik-Butler). 0038-1101/01/$ - see front matter Ó 2001 Published by Elsevier Science Ltd. PII:S0038-110101)00091-0