Abstract:Five percent of Fe-doped ZnO (ZnO:Fe) thin films were deposited on Pt/TiO2/SiO2/Si substrates by a spin-coating method. The films were annealed without (ZnO:Fe-0T) and with a pulsed magnetic field of 4 T (ZnO:Fe-4TP) to investigate the magnetic annealing effect on the resistance switching (RS) behavior of the Pt/ZnO:Fe/Pt structures. Compared with the ZnO:Fe-0T film, the ZnO:Fe-4TP film showed improved RS performance regarding the stability of the set voltage and the resistance of the high resistance state. Tr… Show more
“…It can be clearly seen that the O1s spectrum can be divided into three peaks. For the pure ZnO film, the position of the main O1s peak locates at BE of 530.4 eV resulting from a stoichiometric Zn-O bond, while the rest at 531.9 and 532.2 eV indicate non-lattice oxygen in the ZnO layer and the chemisorbed oxygen, as shown in figure 2(c) [15]. Similarly, for the Hf:ZnO film, the main O1s peak (BE of 529.9 eV) denotes the associated oxygen ions in the ZnO matrix and a BE peak at 531.3 eV, which is attributed to the defects i.e.…”
Section: Resultsmentioning
confidence: 97%
“…Many attempts have been made to improve the RS characteristics of ZnO RRAM devices, including their speed, endurance, power consumption and multi-bit storage capability [12][13][14][15]. An appropriate amount of cobalt dopant in the ZnO resistive layer demonstrated sufficient memory window and switching stability, since the Co element may suppress the formation of abundant native defects in ZnO [13].…”
Section: Introductionmentioning
confidence: 99%
“…Zirconiumdoped ZnO thin film demonstrated a controllable multilevel storage, whereas the device fabricated by a sol-gel method shows poor pulse endurance [14]. Fe:ZnO film annealed in a magnetic field contains more uniform grains and a higher density of oxygen vacancies, which promoted the easier formation of conductive filaments (CFs) along similar paths and enhanced the stability of the switching parameters [15]. However, one of the representative obstacles for the ZnO memristive device is the non-stability in terms of endurance and uniformity.…”
Section: Introductionmentioning
confidence: 99%
“…Normally, the switching behavior of ZnO-based RRAM devices is attributed to the connection/rupture of CFs, which are caused by the migration of oxygen ions in the switching layer [16]. Therefore, doping impurity elements have been reported to be effective for controlling the location of the CFs and hence stabilizing the switching parameters [13][14][15]17]. In fact, it is difficult to acquire a promising endurance property for ZnObased RRAM in industrial application, which relies on the kind and amount of the doping element, film quality and density of defects (such as oxygen vacancies) in the ZnO switching layer.…”
1×1 μm 2 via hole structure ZnO-based resistive random access memory cells are fabricated and the resistive switching behavior is investigated. It can be found that with 5.7% hafniumdoped ZnO film, the memory cell shows remarkable 10 8 pulse endurance. An ON/OFF resistance ratio of at least two orders of magnitude is achieved and the resistive states can remain stable up to 10 4 s. In contrast, a Pt/ZnO/TiN control device presents an unstable resistive switching characteristic and endurance degradation. Compared with pure ZnO film, Hf-doped ZnO film has a relatively smoother surface and larger band gap. X-ray photoelectron spectroscopy analysis indicates that the Hf-doped element induces more non-lattice oxygen ions in the ZnO switching layer. We deduce that the conductive filament forms/ruptures in a fixed path along the Hf atoms. Based on I-V curve fitting and temperature-dependent current measurements, the Pt/Hf:ZnO/TiN device is demonstrated as a Schottky conduction mechanism, which shows reasonable agreement with the possible resistive switching mechanism in the hafnium-doped ZnO memristive device.
“…It can be clearly seen that the O1s spectrum can be divided into three peaks. For the pure ZnO film, the position of the main O1s peak locates at BE of 530.4 eV resulting from a stoichiometric Zn-O bond, while the rest at 531.9 and 532.2 eV indicate non-lattice oxygen in the ZnO layer and the chemisorbed oxygen, as shown in figure 2(c) [15]. Similarly, for the Hf:ZnO film, the main O1s peak (BE of 529.9 eV) denotes the associated oxygen ions in the ZnO matrix and a BE peak at 531.3 eV, which is attributed to the defects i.e.…”
Section: Resultsmentioning
confidence: 97%
“…Many attempts have been made to improve the RS characteristics of ZnO RRAM devices, including their speed, endurance, power consumption and multi-bit storage capability [12][13][14][15]. An appropriate amount of cobalt dopant in the ZnO resistive layer demonstrated sufficient memory window and switching stability, since the Co element may suppress the formation of abundant native defects in ZnO [13].…”
Section: Introductionmentioning
confidence: 99%
“…Zirconiumdoped ZnO thin film demonstrated a controllable multilevel storage, whereas the device fabricated by a sol-gel method shows poor pulse endurance [14]. Fe:ZnO film annealed in a magnetic field contains more uniform grains and a higher density of oxygen vacancies, which promoted the easier formation of conductive filaments (CFs) along similar paths and enhanced the stability of the switching parameters [15]. However, one of the representative obstacles for the ZnO memristive device is the non-stability in terms of endurance and uniformity.…”
Section: Introductionmentioning
confidence: 99%
“…Normally, the switching behavior of ZnO-based RRAM devices is attributed to the connection/rupture of CFs, which are caused by the migration of oxygen ions in the switching layer [16]. Therefore, doping impurity elements have been reported to be effective for controlling the location of the CFs and hence stabilizing the switching parameters [13][14][15]17]. In fact, it is difficult to acquire a promising endurance property for ZnObased RRAM in industrial application, which relies on the kind and amount of the doping element, film quality and density of defects (such as oxygen vacancies) in the ZnO switching layer.…”
1×1 μm 2 via hole structure ZnO-based resistive random access memory cells are fabricated and the resistive switching behavior is investigated. It can be found that with 5.7% hafniumdoped ZnO film, the memory cell shows remarkable 10 8 pulse endurance. An ON/OFF resistance ratio of at least two orders of magnitude is achieved and the resistive states can remain stable up to 10 4 s. In contrast, a Pt/ZnO/TiN control device presents an unstable resistive switching characteristic and endurance degradation. Compared with pure ZnO film, Hf-doped ZnO film has a relatively smoother surface and larger band gap. X-ray photoelectron spectroscopy analysis indicates that the Hf-doped element induces more non-lattice oxygen ions in the ZnO switching layer. We deduce that the conductive filament forms/ruptures in a fixed path along the Hf atoms. Based on I-V curve fitting and temperature-dependent current measurements, the Pt/Hf:ZnO/TiN device is demonstrated as a Schottky conduction mechanism, which shows reasonable agreement with the possible resistive switching mechanism in the hafnium-doped ZnO memristive device.
“…Besides, the HRS conduction is also found to fit well with the Poole–Frenkel conduction mechanism (the insert). The Poole–Frenkel effect is mainly caused by the electric field excited carriers hopping through the trapped states [23], which suggests that there is still a large number of defects in the LaAlO 3 films even after annealing treatment.Fig. 9 a I – V measurement of S3 in different voltage directions.…”
In this paper, the effects of Cu insertion layer and rapid thermal annealing on the resistive switching behaviors of La-based resistive switching access memory (RRAM) devices have been investigated. Compared with the undoped control sample (Cu/LaAlO
3
/Pt), the Cu-embedded devices show higher device yield and reset stop voltage, which indicates that the reliability of La-based RRAM has been effectively improved. However, the unannealed Cu/LaAlO
3
: Cu/Pt RRAM device still suffers from serious dispersion of parameters. It was proved that the RRAM device with Cu insertion layer and annealing treatment exhibits the best resistive switching characteristics such as low forming voltage, high on/off ratio and fine electrical uniformity. These improvements can be attributed to the diffusion of Cu atoms and the formation of Cu nanocrystals (Cu-NCs) after annealing process, since the diffused Cu atoms and the Cu-NCs could enhance the local electric field and weaken the randomness of the formation/rupture of conductive filaments.
The synthesis and characterization of five new and closely related homoleptic iron(II) -ketoiminate complexes is reported. Molecular structures of compounds 1, 2, and 5 were determined by single-crystal XRD, which revealed monomeric four-and sixfold coordination, depending on the functionalized side chain. The stepwise elimination of the ligand from the complex observed by thermogravimetric analysis and the stability in solution are encouraging features for solution-based [a] 1824 processing of hematite thin films. As a representative example, compound 1 was successfully employed in a straightforward spin-coating process. The fabricated iron oxide films were characterized in terms of their structure and phase by XRD and Raman spectroscopy, morphology by SEM, and composition by Rutherford backscattering spectrometry accompanied by nuclear reaction analysis, which revealed the formation of crystalline and stoichiometric α-Fe 2 O 3 films. sition (CSD) techniques of iron oxides such as spin coating, [12] sol-gel processes, [13] and spray pyrolysis [14,15] are of particular interest due to their simple and cost-efficient setup, easy scaleup, and ambient processing conditions. [16] Ideally, precursors for CSD should combine specific characteristics such as high solubility and stability in organic solvents, nontoxicity, and a good compromise between stability to handling in ambient atmosphere and hydrolysis (reactivity) that can enable easy cleavage of ligands to obtain high-purity films on processing. Commonly used iron precursors for CSD of iron oxide are FeCl 2 , [7] FeCl 3 , [14,17] Fe(NO 3 ) 3 , [18,19] and [Fe 4 (mdea) 6 ·6CHCl 3 ]. [20] However, most of these compounds do not feature high solubility and stability in solution, and thus necessitate the use of additives such as amines or long-chain alcohols to enhance the solubility and stabilize the solution. [19,21] Metal alkoxides, for example, [Fe(OtBu) 3 ] 2 , are stable in solution but prone to hydrolysis on exposure to ambient conditions. [22] In the search for suitable precursors for CSD of iron oxide thin films under ambient conditions, the class of metal -ketoiminates is a potential candidate. This ligand class, which has already been successfully applied in metal oxide and nitride CVD and atomic layer deposition (ALD) processes involving metals such as Fe, Zr, Pd, Ga, Ir, Ti, Nb, Ta, and Zn,[23][24][25] features both oxygen and nitrogen coordination, which is a compromise between the highly reactive and thermally unstable nitrogen-bonded metal -diketiminates and the highly stable oxygen-coordinated metal -diketonates. As recently demonstrated by us, iron(II) -ketoiminates are highly promising for gas-phase deposition of iron oxide nanostructures via both ALD and CVD routes at low temperatures. [26] Our next goal was to evaluate this class of compounds for a simple and cost-effective CSD process for iron oxide thin films. As mentioned above, CSD requires precursors with suitable characteristics. The advantageous properties associated with Eur.
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