Mn-doped PZT Research Articles

Improved crystallization, domain, and ferroelectricity by controlling lead/oxygen vacancies in Mn-doped PZT thin films

Pb(Zr0.3Ti0.7)O3-x mol% Mn (PZTM) (x = 0, 1, 2, and 3) thin films with high density and good crystallinity were obtained using a sol-gel method. Improved crystallization, domain, and ferroelectricity through controlling the lead/oxygen vacancies in Mn-doped lead zirconate titanate (PZT) thin films were investigated. Enhanced ferroelectricity and piezoelectricity were obtained in the 1 mol% Mn-doped PZT thin films. According to the Bragg equation, a small amount of Mn replaces the A-site (Pb2+) to achieve donor doping, which is conducive to the movement of domains and enhances the ferroelectric performance and piezoelectric coefficient. The pinning effect leads to reduced ferroelectric performance, which is caused by oxygen vacancies generated by Mn2+ replacing the B-site (Zr4+/Ti4+) during acceptor doping. The research results show that Mn doping is an effective method for improving the ferroelectric performance of PZT thin films.

Intrinsic counterclockwise hysteresis in Mn-doped Pb(Zr,Ti)O3 gated MoS2 field effect transistors

The intrinsic counterclockwise hysteresis induced by the ferroelectric polarization is always concealed in Pb(Zr,Ti)O3 (PZT) gated MoS2 filed-effect transistors (FETs). Here, we observed the well-defined counterclockwise hysteresis in MoS2 FETs with the Mn-doped PZT (Mn-PZT) dielectric layer. The evolution of hysteresis with varying the range of back-gate voltage (Vbg,max) was investigated. The good linear relation was obtained for hysteresis area (〈A〉) with varying Vbg,max. The similar variation tendencies were observed for memory windows (ΔV) of the FET and the coercive voltage (2 Vc) of the PZT film with increasing Vbg,max, indicating the memory windows were defined by the coercive voltages. The hysteresis behavior in this study was thought to be dominant by the intrinsic hysteresis effect of the ferroelectric polarization, which was discussed by the disappearance of the dead layer and the decrease of oxygen vacancies at the PZT/MoS2 interface due to Mn doping.

Enhanced radiation tolerance in Mn-doped ferroelectric thin films

This work investigates the role of Mn-doping of ferroelectric lead zirconate titanate (PZT) thin films exposed to a range of ionizing radiation doses. PZT thin films were fabricated with both undoped and 4% Mn-doped compositions, and the functional response was compared both before and after exposure to gamma radiation doses up to 10 Mrad. A phenomenological model was applied to quantify defect interactions and compare trends in the degradation of the functional response. Mn-doped PZT samples demonstrate reduced magnitude of functional response in non-irradiated samples but exhibit vastly superior radiation tolerance of dielectric and ferroelectric properties across the range of gamma doses studied here. Strong MnZr/Ti″−VO·· defect dipoles pin domain walls, resulting in a lower initial functional response and mitigating the deleterious effects of irradiation on extrinsic contributions to the said response. Piezoelectric response trends as a function of radiation dose are highly nonlinear. The results of this work can be leveraged to engineer next-generation radiation-tolerant ferroelectric materials for applications where high levels of functional response stability are required, especially at elevated ionizing radiation dose.

Highly tunable Mn-doped PZT thin films for integrated RF devices

Modern RF systems have triggered an important and urgent demand for inexpensive voltage controlled capacitors used for a wide range of applications such as tunable antennas or low-noise voltage-controlled oscillators (VCO). Ferroelectric materials have received considerable interest for electrically tunable dielectrics due to their high dielectric constant and large dielectric nonlinearity under dc bias field. Lead zirconate titanate (PZT) ceramics which have been under intense investigation for various industrial domains including micro-electro-mechanical systems (MEMS), non-volatile memories, and high-k capacitors, are especially well-known candidate materials due to their unequalled ferroelectric properties and stability in device operating ranges. However, reported voltage tunability of PZT films is relatively low (~35%@4GHz) and remains insufficient for microwave tunable devices. Therefore, much attention has been focused on the PZT modification by adding a small amount of dopants. Shao et al., studied strontium-doped PZT (PSZT) thin films and achieved a tunability of 48% @1MHz. More recently, Hu et al. reported a tunability of 65%@10kHz for lanthanum-modified PZT (PLZT) films. In the presented study, effect of manganese (Mn) doping on electrical properties of PZT (PMZT) thin films has been investigated. Metal/insulator/metal (MIM) capacitors using PZT-based thin films and ruthenium (Ru) top electrodes were processed on platinized (Pt) silicon wafers by a sol gel method. Dielectric properties of PMZT thin films were studied by varying the dopant amount and compared to those of pure PZT layers. At this end, on-wafer electrical measurements were conducted with a particular attention on leakage current characterization and RF measurements under DC bias voltage. We have shown that leakage current density decreased from 6.5 μA/cm2 to 1 μA/cm2 at 850kV/cm by doping PZT with Mn. Observed conduction mechanisms will be discussed in detail in the full-length paper. Moreover, developed PZT-based thin films exhibit high dielectric strengths achieving 2.1MV/cm and outstanding tunability as high as 85% (~7:1) @1GHz at bias voltage of 20V. Thus, PMZT tunability is among the highest ones reported in the literature for PZT-derived thin films but also for other piezoelectric materials. Indeed, in comparison, the tunability of BST-based materials, typically studied for voltage tunable applications, does not exceed 5:1. These remarkable results indicate that Mn-doped PZT thin films are promising candidates for RF tunable capacitors.

Enhancement of pyroelectric properties of composite thick films using Mn-doped PZT

The effects of manganese (Mn) doping content in lead zirconate titanate (PZT) on PZT/polyvinylidene-trifluorethylene copolymer (P(VDF-TrFE)) composite thick films have been studied in this paper. Various Mn doped Pb(Zr0.3Ti0.7)1−xMnxO3 (PZTMx, x=0, 1, 2, 3mol%) were mixed with P(VDF-TrFE) and coated on indium-tin-oxide (ITO)-coated glass substrates to fabricate the PZT/P(VDF-TrFE) composite films. The microstructures of PZTMx particles and the composite films have been investigated by scanning electron microscopy and X-ray diffraction techniques. The dielectric and pyroelectric measurements were carried out to study the effects of Mn doping content on the electric properties of composites. It was found that the electric properties of composites show great dependence on Mn doping content in PZTMx ceramic filler. Especially, the pyroelectric coefficient and detectivity figure of merit (FD) of the PZTM2/P(VDF-TrFE) composite film reached 113μC/m2K and 1.77×10−5Pa−1/2, which increased about 26% and 35% than the pure PZT/P(VDF-TrFE) composite film, respectively.

Fabrication of Mn Doped PZT for Ceramic-Polymer Composites

Fabrication of Mn Doped PZT for Ceramic-Polymer Composites

Influence of Atmospheric Annealing on the Conductivity of Mn-Doped PZT Ceramics

Conductivity measurements were carried out on Mn-doped PZT ceramics in order to investigate the changes in defect chemistry with annealing, by identifying the charge carriers such as lead or oxygen vacancies. PZT compositions were prepared by sol-gel method in rhombohedral region Pb(Zr0.56 Ti0.44)O3 with Mn contents 0.4, 0.8, 1.5 and 2 wt.%. Nano-sized powder (~21nm) was obtained after calcination and bulk density values of >98% were achieved upon sintering. It was found that nitrogen annealing reduced the electrical conductivity strongly as compared to oxygen and air annealing and the possible charge carriers were single ionised oxygen vacancies along with and vacancies.

Bipolar strain hysteresis of poled composites with Nd–Mn-doped PZT fibres

Nd–Mn-doped PZT fibres were produced using the sol–gel process. The PZT was doped with 2 mol% neodymium and an amount of 1.1 mol% or 0.75 mol% manganese. The fibres were investigated with respect to microstructure, composition after sintering and phase content. Strain and polarisation were measured after imbedding the fibres in a polymer matrix. The resulting 1–3-composites were poled with constant electric field. Measurements of strain and polarisation were done using a sinusoidal voltage of high amplitude. Instead of a shifted strain hysteresis (butterfly loop) an asymmetric strain–field relation was observed. The asymmetry depends on the direction of the applied voltage. For the half wave with voltage parallel to former poling voltage the strain curve is linear. For the other half wave the strain curve inflates and there is a region with no change of strain. Possible explanations for the asymmetric strain behaviour are discussed.

EXAFS study on the site preference of Mn in perovskite structure of PZT ceramics

Synchrotron extended X-ray absorption fine structure (EXAFS) measurements at the Mn K edge were performed on Mn-doped PZT ceramics with Mn concentrations of 0.5, 1.0 and 2.0 mol%. The Fourier transforms of EXAFS structures from all samples are similar and agree well with the model of Mn substituting on the Ti/Zr site (i.e. the B site of the perovskite ABO 3 structure). This shows that Mn predominantly substituted for Ti/Zr in the range of concentration under study.

EFFECT OF MANGANESE DOPING ON THE ELECTRICAL CHARACTERISTICS OF SOL-GEL DERIVED LEAD ZIRCONATE TITANATE THIN FILMS

ABSTRACT Manganese (Mn) doped Pb(Zr,Ti)O3 thin films were prepared by sol-gel technique and their dielectric, ferroelectric and dc leakage current characteristics were studied in detail. There was a decrease in the dielectric constant, phase transition temperature and increase in the leakage current with the increase in the concentrations of the Mn ions. The decrease in the transition temperature is due to the breaking down of translation symmetry of the polarization, thereby establishing the local dipole moments on suppressing the long-range ferroelectric order. The dielectric dispersion was large for the higher concentration of Mn ions in PZT thin films at lower frequencies and is attributed to the space charge accumulation. The loss tangent initially increases and then decreases with the increase in the Mn ions concentrations indicating the disappearance of the conducting boundary layers. The undoped and Mn doped PZT thin films exhibit the hysteresis loops which confirms the ferroelectric behavior. The dc leakage current conduction mechanism obeyed to space charge limited mechanism and the activation energy calculated from the dc leakage current is attributed to shallow traps.

Effects of dopants on properties of PZN-PSN-PMN-PZT ceramics

In order to obtain high Qm ceramics, different additives including MnO2, Fe2O3 and K2CO3 were added into the base PZT composition of xPb(Zn0.2Sn0.3Mn0.5)1/3 Nb2/3O3-(1−x)Pb(Zr0.5T0.5)O3. The mechanical quality factor Qm increased while the piezoelectric constant decreased to some degree as MnO2 was added alone. Although apparent decreasing was observed in piezoelectric constant d33 after MnO2 and Fe2O3 were added simultaneously, the mechanical quality factor Qm was kept at the same level as before. The values of d33 and Qm decreased dramatically as K2CO3 was added in combination with MnO2 and Fe2O3. The structure of grain boundary was damaged and more defects were generated by low valence K adding in this multi-impurified PZT solid. Mn doped sample presented a wide range of sintering temperature. The properties parameters of Mn doped PZT are listed as follows: piezoelectric constant d33=256pC/N, mechanical quality factor Qm=2079, coupling coefficient Kp=0.53, Coercive field Ec=22.5kV/cm, Cure Temperature Tc=286°C. These parameters show that Mn-doped PZT ceramics are suitable for application in high Qm and transmitting materials.

Effects of Zr/Ti ratio on structural, dielectric and piezoelectric properties of Mn- and (Mn, F)-doped lead zirconate titanate ceramics

The influence of the Zr/Ti ratio on the piezoelectric properties of (Mn and 1 at.% F)-doped PZT and Mn-doped PZT ceramics is investigated. Lead zirconate titanate ceramics (PZT) are prepared from chemical route based on co-precipitation of oxalates and hydroxides. Structural analysis (XRD) and measurement of electrical properties were carried out. Scanning electron microscopy is used to determine the grain size of the materials. The valency states of Mn in fluorinated PZT ceramics are studied by Electron Spin Resonance (ESR). From the experimental results, the F O substitution increases the piezoelectric activity at the morphotropic phase boundary (MPB) and the Q m in the rhombohedral region. In the (Mn, F)-co-doping case, the high-piezoelectric activity found at the MPB is due to an electron transfer mechanism that involved the three valency states of manganese whereas the improvement of Q m can be explained by the valence state of manganese and the dipole defect concept.

Influence of the Niobium or Fluorine Dopant Concentration on the Properties of Mn-Doped Lead Zirconate Titanate Ceramics

In this paper, we report on the effect of donor addition (Nb5+ or F-) on the electrical and piezoelectric properties and crystallographic characteristics of Mn-doped lead zirconate titanate (PZT) ceramics. Samples were prepared chemically by coprecipitation of oxalates and hydroxides. The niobium ion was incorporated in the B site whereas the fluorine ion was introduced in the anionic site. Structural analysis (XRD) and measurement of electrical properties were carried out. Electron spin resonance was used to determined the valency states of manganese in PZT ceramics. From the experimental results, the F–O substitution decreases the amount of oxygen vacancies in the Mn-doped PZT, and the valency states remain unchanged. However, a small number of oxygen vacancies may exist in PZT doped with 1 at.% manganese and 2 at.% fluorine. In the (Mn,Nb) co-doping case, the valency states vary from 4+ to 2+ and the number of oxygen vacancies is lower or even almost equal to zero. Thus the electroneutrality is achieved by lead vacancies.

Pyroelectric Arrays: Ceramics and Thin Films

Pyroelectric infra-red detectors have been of-interest for many years because of their wide wavelength response, good sensitivity and lack of need for cooling. They have achieved a wide market acceptance for such applications as people sensing, IR spectrometry (especially for environmental protection) and flame/fire protection. Arrays of such detectors, comprising a pyroelectric material interfaced to an application specific integrated circuit for signal amplification and read out, provide an attractive solution to the problem of collecting spatial information on the IR distribution in a scene and a range of new applications are appearing for such devices, from thermal imaging to people sensing and counting. The selection of the best material to use for such a device is very important. Because all polar dielectrics are pyroelectric, there is a very wide range of such materials to choose. The performance of a pyroelectric IR sensor array can be derived from the physics of their operation and figures-of-merit (FoM) defined that will describe the performance of a material in a device, in terms of its basic pyroelectric, dielectric and thermal properties. These FoM and their appropriateness for the array application are reviewed. Large arrays of small detectors are best served by the use of pyroelectric materials with permittivities between 200 and 1000, depending upon the element size and the element thermal conductance, and a maximised FoM F D = p{c′ (e e o tan δ)1/2}. Such properties are found in ferroelectric perovskite ceramics and a wide range have been explored for their use in pyroelectric arrays. These include materials based on compositions in the PbZr x Ti1 − xO3 (PZT) system, for example close to PbZrO3, with Curie temperatures well above ambient. Examples of the ways in which these materials can be modified by doping to optimise their FoM and other important properties such as electrical resistivity are given and the physics operating behind this discussed. The performances and costs of uncooled pyroelectric arrays are ultimately driven by the materials used. For this reason, continuous improvements in materials technology are important. In the area of bulk ceramics, it is possible to obtain significant improvements in both production costs and performance though the use of tape-cast, functionally-gradient materials. Finally, the use of directly-deposited ferroelectric thin films on silicon ASIC’s is offering considerable potential for low cost high performance pyroelectric arrays. The challenges involved in developing such materials will be discussed, especially from the aspect of low temperature deposition and other fabrication issues, such as patterning. Sol gel deposition provides an excellent technique for thin film growth and Mn-doped PZT films can be grown at 560∘C with a FoM F D exceeding those of many bulk materials.

Low fatigue lead zirconate titanate-based capacitors modified by manganese for nonvolatile memories

We have investigated the effects of Mn doping on the ferroelectric properties of Pb(Zr0.3Ti0.7)O3 (PZT) thin films on substrates Pt/Ti/SiO2/Si. Small amount of Mn-doped (≤1mol%) PZT (PMZT) showed almost no hysteretic fatigue up to 1010 switching bipolar pulse cycles, coupled with excellent retention properties. We present evidence that while a low permittivity interfacial layer forms between the Pt electrode and PZT films, this does not occur in PMZT. We propose that Mn dopants are able to reduce oxygen vacancy mobility in PZT films and Mn2+ ions consume the oxygen vacancies generated during repeated switching, forming Mn4+ ions. These mechanisms are probably responsible for their low observed fatigue characteristics.

Effects of Mn doping on the ferroelectric properties of PZT thin films

The effects of Mn doping on the ferroelectric properties of Pb(Zr0.3Ti0.7)O3 (PZT) thin films on Pt/Ti/SiO2/Si substrates have been investigated. The composition of the PZT and Mn doping level are Pb(Zr0.3Ti0.7)1−xMnxO3 (x = 0,0.2,0.5,1,2,4 mol%). The PZT thin films doped with a small amount of Mn2+ (x ⩽ 1) showed almost no hysteretic fatigue up to 1010 switching bipolar pulse cycles, coupled with excellent retention properties. However, excessive additions of manganese made the fatigue behaviour worse. We propose that the addition of small amounts of Mn is able to reduce the oxygen vacancy concentration due to the combination of Mn2+ and oxygen vacancies in PZT films, forming Mn4+ ions. The interfacial layer between the Pt electrode and PZT films and Mn-doped PZT (x = 4) was detected by measuring the dielectric constant of thin films of different thickness. However, this interfacial layer was not detected in Mn-doped PZT (x = 1). These observations support the concept of the preferential electromigration of oxygen vacancies into sites in planes parallel to the electrodes, which is probably responsible for the hysteretic fatigue.

Improved ferroelectric and pyroelectric properties in Mn-doped lead zirconate titanate thin films

We have investigated the effects of Mn doping on the ferroelectric and pyroelectric properties of Pb(Zr0.3Ti0.7)O3 (PZT) thin films on substrates Pt/Ti/SiO2/Si. The Mn-doped (1 mol %) PZT (PMZT) showed almost no hysteretic fatigue up to 1010 switching bipolar pulse cycles, coupled with excellent retention properties. We present evidence that while a low permittivity interfacial layer forms between the Pt electrode and PZT films, this does not occur in PMZT. We propose that Mn dopants are able to reduce oxygen vacancy mobility in PZT films and Mn2+ ions consume the oxygen vacancies generated during repeated switching, forming Mn4+ ions. These mechanisms are probably responsible for their low observed fatigue characteristics. Mn doping brings additional benefits to the electrical properties of PZT films. The relevant pyroelectric coefficients (p) of a 700 nm thick film are 3.52×10−4 C m−2 K−1 and detectivity figures of merit FD=3.85×10−5 Pa−0.5 at 33 Hz for Mn-doped PZT, compared with p=2.11×10−4 C m−2 K−1 and FD=1.07×10−5 Pa−0.5 for the undoped PZT films. This means that the Mn-doped PZT thin films are excellent candidates as device materials for both memory and pyroelectric applications.

Hysteretic properties of Mn-doped Pb(Zr,Ti)O 3 thin films

Pb(Zr,Ti)O 3 (PZT 30/70) and Mn-doped Pb(Zr,Ti)O 3 (PMZT 30/70) thin films have been fabricated on Pt/Ti/SiO 2/Si substrates by a chemical solution deposition technique. The experiments found that the addition of Mn in PZT thin films greatly improves the ferroelectric properties of thin films. It is demonstrated that the Mn-doped (1 mol%) PZT showed fatigue-free characteristics at least up to 10 10 switching bipolar pulse cycles under 10 V and excellent retention properties. The Mn-doped PZT thin films also exhibited well-defined hysteresis loops with a remnant polarization (Pr) of 34 μC/cm 2 and a coercive field (Ec) of 100 kV/cm for the thickness of 300 nm. Dielectric constant and loss (tan δ) for Mn doped PZT thin films are 214 and 0.008, respectively. These figures compare well with or exceed the values reported previously. In this paper, the mechanism by which Mn influences on the ferroelectric properties of PZT thin films has also been discussed.

Improved Ferroelectric Properties in Mn-Doped PZT Thin Films

We have investigated the effects of Mn doping on the ferroelectric properties of Pb(Zr0.3Ti0.7)O3 (PZT) thin films on substrates Pt/Ti/SiO2/Si. The Mn-doped (1 mol%) PZT (PMZT) showed almost no hysteretic fatigue up to 1010 switching bipolar pulse cycles, coupled with excellent retention properties. We present evidence that while a low permittivity interfacial layer forms between the Pt electrode and PZT films, this does not occur in PMZT. We propose that Mn dopants are able to reduce oxygen vacancy mobility in PZT films and Mn2+ ions consume the oxygen vacancies generated during repeated switching, forming Mn4+ ions. These mechanisms are probably responsible for their low observed fatigue characteristics.

Sol-gel PZT and Mn-doped PZT thin films for pyroelectricapplications

Thin films of ferroelectric lead zirconate titanate(PbZr0.3Ti0.7O3 PZT30/70) and manganese-doped lead zirconatetitanate ((Pb(Zr0.3Ti0.7)1-xMnx)O3, where x = 0.01,PM01ZT30/70; and x = 0.03, PM03ZT30/70) have been prepared using sol-gelprocessing techniques. These materials can be used as the pyroelectric thinfilms in uncooled infrared detectors. The thin films were prepared via asol-gel route based on a hybrid solvent of methanol and ethanol with aceticacid, ethanolamine and ethylene glycol as additives. The final solution isnon-moisture sensitive and stable. Films deposited on Pt/Ti/SiO2/Sisubstrates and annealed on a hot plate at 500-530 °C for a fewminutes were seen to fully crystallize into the required perovskite phase andshowed excellent ferroelectric behaviour, demonstrated by reproduciblehysteresis loops (Pr = 33-37 µC cm-2, Ec( + ) = 70-100 kV cm-1, Ec(-) = -170 to -140 kV cm-1). Thepyroelectric coefficient (p) was measured using the Byer-Roundy method. At20 °C, p was 2.11×10-4 C m-2 K-1 for PZT30/70,3.00×10-4 C m-2 K-1 for PM01ZT30/70 and2.40×10-4 C m-2 K-1 for PM03ZT30/70 thin films. Thedetectivity figure-of-merit (FD) was 1.07×10-5 Pa-0.5 forPZT30/70, 3.07×10-5 Pa-0.5 for PM01ZT30/70 and1.07×10-5 Pa-0.5 for PM03ZT30/70. These figures compare wellwith values reported previously.