A series of technical data for preparing PbTiO3 ferroelectric thin films and their applications to some electronic devices have been presented. PbTiO3 thin films having considerably good ferroelectric properties have been obtained by rf sputtering or CVD. Maximum dielectric constant and remanent polarization are about 200 and 27μC/cm2, respectively. Several attempts to fabricate electronic devices such as nonvolatile memory, infrared sensor, ultrasonic sensor and low-threshold electroluminescent devices have been also carried out.

Preparation and basic properties of PbTiO3 ferroelectric thin films and their device applications

Ferroelectric PbTiO3 thin films and their application

Asymmetric rocking curve study of the crystal structure orientations for BaTiO3 thin films grown by pulsed laser deposition

Interface states in the ferroelectric-semiconductor junction have been investigated from analyses of DLTS andC-V data. Two trap levels are located at 0.21 and 0.36 eV below the conduction band near the silicon side of the interface in the MFS (Metal-Ferroelectric-Semiconductor) structure. The interface states density has been drastically reduced by putting an oxide layer between ferroelectric and semiconductor with certain heat treatment in H2 atmosphere at 500 °C. It has been found that the MFMOS (Metal-Ferroelectric-Metal-Oxide-Semiconductor) structure shows the least interface states density (less than 1011cm−2eV−1) with the maximal dielectric constant of PbTiO3 thin films.

https://link.springer.com/content/pdf/10.1007/BF00617981.pdf

A study of electronic states near the interface in ferroelectric-semiconductor heterojunction prepared by rf sputtering of PbTiO3

Graded ferroelectric (GF) structures were obtained by successive deposition of Pb1−3y/2Lay(Zr0.4Ti0.6)O3 films with different La contents on Pt/TiO2Si substrates. The method used for deposition was sol gel. The final structure consists of four layers, starting from the Pt electrode to the top gold electrode: (1) no La; (2) 4% La; (3) 8% La; and (4) 12% La. Ferroelectric properties of the GF structure were investigated, and an anomalous shift of the hysteresis loop along the polarization axis was found. The sense of this shift depends on the initial direction of the ferroelectric polarization. The presence of hysteresis displacement “up” or “down” can be explained if the presence of a built-in charge in the GF structure is admitted. The built-in potential produced by this charge is computed using a simple theoretical model.

Ferroelectric properties of Pb1−3y/2Lay(Zr0.4Ti0.6)O3 structures with La concentration gradients

A pyroelectric infrared sensor made of PbTiO3 ferroelectric thin film constructed on Si wafer has been developed. Pyroelectric output signal is amplified in current mode by a bipolar transistor which is devised on the same Si wafer. The device performance is much improved in high frequency region as compared with that of previous FET mode monolithic sensors, and it can be operated up to a few tens kHz region. Current responsivity of the PbTiO3 film has been also increased by reducing a heat capacity of the sensitive area and the output voltage of the device is 1.1 mV under the illumination of 120 mW/cm2 at 1 kHz which is one order of magnitude larger than that of the previous FET mode structure attached directly to Si wafer. The detectivity is ~105 cm √Hz/W with bandwidth of 1 Hz at chopping frequency of 1 kHz. The rise time of the response measured under CO2 laser pulse irradiation is about 2.5 µs.

Pyroelectric Infrared Sensor Using PbTO3Thin Film

IR-OPFET having a structure of PbTiO3 thin film gate on Si FET has been fabricated. The pyroelectric property of a tiny PbTiO3 thin film provides a high speed infrared sensitivity with a wide wavelength range at room temperature. A typical performance as an IR-OPFET is that voltage responsivity Rv and detectivity D* are 390 V/W and 3.5×105 cm√Hz/W, respectively, at 20 Hz under infrared irradiation coming through a Ge filter from an incandenscent lamp. The rise time of the response measured by one shot of CO2 laser pulse is estimated to be about 3.5 µsec.

Hiroyuki Seto

Papers

Pyroelectric Infrared Sensor Using PbTO3Thin Film

IR-OPFET: Infrared Sensor Using PbTiO3Pyroelectric Film

IR-OPFET: Infrared Sensor Using PbTiO3 Pyroelectric Film