Yafeng Luo

Structural, ferroelectric, dielectric, and magnetic properties of BiFeO3/Bi3.15Nd0.85Ti3O12 multilayer films derived by chemical solution deposition

BiFeO3/Bi3.15Nd0.85Ti3O12 (BFO/BNdT) multilayer films have been grown on Pt-coated silicon substrate by chemical solution deposition. Using Bi3.15Nd0.85Ti3O12 as an inducing layer, ferroelectric properties of BiFeO3 were enhanced significantly. The 2Pr and coercive electric field of the Pt/BFO/BNdT/Pt capacitor were about 22.1 μC/cm2 and 50 kV/cm, respectively. The dielectric constant and the dissipation factor of the multilayer were 373 and 0.05 measured at 105 Hz, respectively. The multilayer capacitors not only exhibited excellent fatigue resistance without polarization reduction after 1010 switching cycles but also showed lower leakage current density (around the order of 10−9–10−7 A/cm2) and negligible data loss due to imprint. The magnetic hysteresis indicated that the multiplayer was antiferromagnetic and the saturated magnetization was about 2.47 emu/cm3.

Characterization of Pt/Bi3.15Nd0.85Ti3O12/HfO2/Si structure using a hafnium oxide as buffer layer for ferroelectric-gate field effect transistors

We have investigated the structural and electrical properties of metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with Bi3.15Nd0.85Ti3O12 (BNdT) thin film deposited on Si and hafnium oxide (HfO2)/Si substrates. Microstructural analysis reveals the formation of well-crystallized BNdT perovskite film and good interface between BNdT film and HfO2 buffer layer. Pt/BNdT/HfO2/Si structure exhibits a memory window of 1.12 V at an operation voltage of 3.5 V. The width of memory window for the MFIS structure varies with increasing thickness of HfO2 layer, and 4-nm-thickness is optimum. The results from the fatigue test indicate a slight degradation of the memory window after 1010 switching cycles. These properties are encouraging for the development of ferroelectric memory transistors.

Fabrication and Properties of

Metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with 400-nm-thick Bi_3.15Nd_0.85Ti₃O₁₂ (BNdT) ferroelectric film and 4-nm-thick hafnium oxide (HfO₂) layer on silicon substrate have been fabricated and characterized. It is demonstrated that the Pt/Bi_3.15Nd_0.85Ti₃O₁₂/ HfO₂/Si structure exhibits a large memory window of around 1.12 V at an operation voltage of 3.5 V. Moreover, the MFIS memory structure suffers only 10% degradation in the memory window after 10¹⁰ switching cycles. The retention time is 100 s, which is enough for ferroelectric DRAM field-effect-transistor application. The excellent performance is attributed to the formation of well-crystallized BNdT perovskite thin film on top of the HfO₂ buffer layer, which serves as a good seed layer for BNdT crystallization, making the proposed Pt/Bi_3.15Nd_0.85Ti₃O₁₂/ HfO₂/Si suitable for high-performance ferroelectric memories.

\hbox{Pt}/\hbox{Bi}_{3.15}\hbox{Nd}_{0.85} \hbox{Ti}_{3}\hbox{O}_{12}/\break\hbox{HfO}_{2}/\hbox{Si}

Neodymium and manganese-doped BiFeO3 — (Bi0.95Nd0.05)(Fe0.95Mn0.05)O3(BNFMO) ferroelectric film and HfO2 layer with different thickness were fabricated using metal-organic decomposition and atomic layer deposition (ALD) method, respectively. Metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with 200 nm thick BNFMO and 5 nm thick HfO2 layer on silicon substrate have been prepared and characterized. It is found that there is no distinct interdiffusion and reaction occurring at the interface between BNFMO/HfO2 and HfO2/Si. The capacitance–voltage (C–V) and leakage current properties of Pt/HfO2/Si capacitors with different HfO2 thickness were studied. The MFIS structure showed clockwise C–V hysteresis loops due to the ferroelectric polarization of BNFMO. The maximum memory window is 5 V. The leakage current of the Pt/BNFMO/HfO2/Si capacitor was about 2.1 × 10-6 A/cm2 at an applied voltage of 4 V.

Structure for Ferroelectric DRAM (FEDRAM) FET

This paper [ibid., vol. 30, no. 5, pp. 463?465, May 2009] is withdrawn at the request of the authors. The lead author has made errors in the IEEE member grades of the coauthors and not all the coauthors have prior knowledge of the submission by the lead author.

ATOMIC LAYER DEPOSITION HfO2 FILM USED AS BUFFER LAYER OF THE Pt/(Bi0.95Nd0.05)(Fe0.95Mn0.05)O3/HfO2/Si CAPACITORS FOR FeFET APPLICATION

Ferroelectric B3.15Nd0.85Ti3O12 (BNdT) thin films were deposited on SrTiO3/Si, HfO2/Si and Si substrates respectively by sol-gel process. The electrical properties were studied for Metal-Ferroelectric-Semiconductor (MFS) and Metal-Ferroelectric-Insulator-Semiconductor (MFIS) capacitors. The MFIS structure exhibited well clockwise capacitance-voltage hysteresis loops due to the ferroelectric polarization of BNdT thin film achieved. The maximum memory windows were 3.2 V and 4.7 V, respectively for BNdT deposited on SrTiO3 and on HfO2 buffer layers. In comparison, the memory window of the thin film on Si substrate was 2.8 V. The leakage current of the structure with a buffer layer was much lower than that without a buffer layer. The leakage current of the thin film deposited on SrTiO3/Si was of the order of 10-9-10-8 A/cm2. The electrical properties of the MFIS structures were improved. The results show that the BNdT based MFIS capacitor is a promising candidate for ferroelectric field effect transistor (FeFET).

Withdrawal of "Fabrication and Properties of

Ferroelectric field effect transistor (FeFET) is a promising candidate in nonvolatile memory application due to its fast read/write speed, nondestructive readout, and low power consumption. Since the poor retention characteristic can be improved by introducing insulator buffer layers between gate layer and FET channel region, more and more attentions are devoted to the realization and optimization of this novel memory device [1]. Traditional ferroelectric materials, such as PZT [2, 3] and SBT [4] based FeFETs are extensively studied and reported in the past decades. Recently, Nd-doped Bismuth Titanate B3.15Nd0.85Ti3O12 (BNdT) with a large remnant polarization (2Pr=103µC/cm2) and outstanding fatigue endurance was reported by Chon et al. [5], and many ferroelectric applications are being processed based on this brand new ferroelectric material [6, 7]. In this letter, we fabricated a BNdT based FeFET for the first time. The fundamental structural and electrical properties are investigated correspondingly.

\hbox{Pt}/\hbox{Bi}_{3.15}\hbox{Nd}_{0.85}\hbox{Ti}_{3}\hbox{O}_{12}/\hbox{HfO}_{2}/\hbox{Si}

Reactive ion etching (RIE) and ion beam etching (IBE) were used to etch the Bi3.15Nd0.85Ti3O12 (BNdT) ferroelectric layer and top electrode (TE), respectively, for ferroelectric random access memory (FeRAM) applications. The effect of dry etching on the ferroelectric properties of Pt/BNdT/Pt capacitors and the film etching mechanism were investigated. After TE etching, the remanent polarization (2Pr) of capacitors decreased through the charging effect, but was recovered by rapid thermal annealing (RTA). A distinct polarization suppression of the capacitors was observed after BNdT layer dry etching owing to the large amount of ions accumulated in the electrode/film interface and within the films. The property damage could be recovered after long-time furnace annealing. The capacitor property rejuvenation was complete even after 1010 switching cycles of fatigue test. The capacitor size effect and recovery of the ferroelectric properties after film etching process were also studied.

Structure for Ferroelectric DRAM (FEDRAM) FET"

Anti-ferromagnetic BiFeO₃/Bi_3.15Nd_0.85Ti₃O₁₂ (BFO/BNdT) multilayer films with remnant polarization of 22.1 ¿C/cm² have been fabricated by sol-gel method on Pt (100)/Ti/SiO₂/Si (100) substrate. X-ray diffraction analysis indicates high (110) orientation and a relatively degree of (111) orientation in the multilayer achieved. The dielectric constant and the dissipation factor of the multilayer are 373 and 0.05 measured at 10⁵ Hz, respectively. The multilayer film exhibits little polarization fatigue(<5%) upon 10¹⁰ switching cycles. The enhanced ferroelectric properties are mostly ascribed to the coupling reaction between the BFO and BNdT thin films, and the BNdT layer induces the crystallization of BFO thin film.