Yongyuan Zang

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.

Resistive switching behavior in diamond-like carbon films grown by pulsed laser deposition for resistance switching random access memory application

In this paper, nonvolatile bipolar resistive memory effects were observed in nitrogen doped diamond-like carbon (DLC) thin films prepared by a pulsed laser deposition technique. It is observed that the fabricated Pt/Ti/DLC/Pt structure exhibits good memory performances with an ON/OFF ratio >10, data retention time >104 s, and low operation voltage (<1.5 V). The current mechanism is fitted by Ohmic and space charge limited conduction laws in low resistance state and high resistance state scenarios. The formation/rupture of metal filaments is due to the diffusion of the titanium ions.

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}

ABSTRACT The metal-ferroelectric-insulator-semiconductor (MFIS) structure were fabricated and investigated. The Bi3.15Nd0.85Ti3O12 (BNdT) thin films were deposited on the Si substrates by sol-gel process with HfO2, SiO2 and Si3N4 as the buffer layers. Perovskite crystalline was obtained and the ferroelectric polarization-voltage (P-V) hysteresis was studied for the Pt/BNdT/Pt/Ti/SiO2/Si(100) and Pt/BNdT/HfO2/Si(100) capacitors. Good interfacial properties were examined between the BNdT thin film and Si substrate. Memory windows of the Pt/BNdT/HfO2/Si(100) structure were in the range of 0.9v-1.2v when the thickness of the HfO2 buffer layer varied from 3 nm to 5 nm, exhibiting a considerable memory effect in the capacitors.

Structure for Ferroelectric DRAM (FEDRAM) FET

ABSTRACT B3.15Nd0.85Ti3O12 (BNdT) thin films were prepared on Pt(100)/Ti/SiO2/Si(100) substrate by sol-gel process. Perovskite crystalline was observed in the thin films achieved, and the grain size of the thin film was about 200 nm in diameter with sharp and clear boundaries between different films and the Pt electrodes. Well-saturated polarization-voltage (P-V) switching curves were examined in the BNdT thin films. The remnant polarization and the coercive field of the BNdT thin films annealed at 750°C were 43 μ C/cm2 and 66 kv/cm at an applied voltage of 8v, respectively. The dielectric constant and the dissipation factor were 583 and 0.07 respectively, measured at 100 KHz.

INTERFACE STUDIES AND ELECTRONIC PROPERTIES OF SILICON BASED Nd-DOPED BISMUTH TITANATE

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.

MICROSTRUCTURE AND DIELECTRIC PROPERTIES OF ND-DOPED BISMUTH TITANATE

Enhanced photovoltaic performance of BiFeO3 (BFO) material by utilizing graphene and carbon nanotubes (CNT) as transparent electrodes is compared for the first time. The short circuit current density and open circuit voltage are measured to be 34μA/cm2, 2.4μA/cm2, 0.27V and 0.31V by utilizing graphene and carbon nanotubes (CNT), respectively, much higher than the value reported in polycrystalline BFO. A theoretical model considering ferroelectric polarization, interface state, and energy band bending are constructed to investigate the carrier transportation behavior of the BFO solar cell. A Photochromic film is also proposed as an interesting application by using graphene/BFO/Pt solar cell as a photo detector.

Withdrawal of "Fabrication and Properties of

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).

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

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.

Structure for Ferroelectric DRAM (FEDRAM) FET"

ABSTRACT Sr1−xBaxBi4Ti4O15 (SBBT) thin films with various Ba2+ contents (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by Sol-Gel technique. Based on the precursors with different x values, SBBT graded thin films with gradients in composition were fabricated using a special heating treatment procedure below 800°C. The band edge absorption of SBBT graded thin films was between that of BBTi and SBTi films in the wavelength of 260 nm ∼350 nm. And the absorption peak position was about 469.2 nm and 611.8 nm, respectively. The average transmission ratio was about 76%, which was higher than that of mono-composition films. The optical band gap energy (Eg) of SBBT graded film was about 4.15 eV. Annealing conditions also have a great influence on the optical properties of the graded thin films. With the increase of annealing temperatures, the band edge absorption of SBBT graded thin film red-shifted and the optical band gap energy deceased monotonously.