Study On The Preparation And Magnetoelectric Coupling Effect Of Oxide Composite Heterostructure

The magnetoelectric coupling effect has a great prospect in energy conversion,sensing signals and monitoring of magnetic?electric?fields,ferromagnetic and ferroelectric materials can be used for the preparation of Multi-state memory.It can increase the storage rate of information to save storage space.But,It is difficult to realize the magnetoelectric coupling effect of single-phase multi-ferrous material at room temperature.The researchers proposed the magnetoelectric composite material?2-2 structure heterostructures film?.The advantages of the 2-2 structure is that it is uniform and orderly interface,but due to clamping effect the magnetoelectric coupling effect is weak.In this paper,a method for eliminating substrate limitations is proposed to overcome the disadvantages of 2-2structure.Through this method,we can get high quality transferable quasi-two-dimensional heterostructures films.Compared with the traditional film,these quasi-two-dimensional nano film without rigid substrate constraints,the piezoelectric properties and the magnetoelectric coupling effect of the film are improved.In this paper,a series of studies have been carried out from the preparation of oxide heterostructures thin films to substrate transfer and prototype device preparation.First,the preparation process of the BaTiO₃/CoFe₂O₄/MgO film was optimized on the STO substrate by PLD.The growth parameters of each layer were optimized.The growth parameters of MgO and CFO films were basically the same.The laser energy density is higher,the RMS of MgO and CFO are 0.21nm and 0.19nm,respectively.The growth of BTO film is easier to require less energy,and the background vacuum is also relatively low,RMS is 0.31nm.Second,the film transfer process was optimized,the thickness of the film belongs to the nanometer scale The transferable BTO-CFO heterostructures thin film has been obtained by solution ecthing method.Three different transfer methods were proposed:Au protection transfer,PDMS protection transfer and PMMA protection transfer.Using PMMA,10%?NH₄?₂SO₄ solution at 80?C.Under the conditions of corrosion,we finally got 5×5mm complete transferable BTO-CFO heterostructures thin film,which was transferred to Si or Mica,the transferred film retains the excellent quality of the original sample.Third,study on the properties of thin films,The ferroelectricity and ferromagnetism of BTO and CFO were tested respectively.after the properties of bilayer films were studied,these quasi-two dimensional nanomembranes showed enhanced ferroelectric properties over not transferred thin films.The BTO film is transferred to the HEMT gate to make the threshold voltage drift 0.5V.Besides,the weak magnetic field detector is prepared based on the magnetoelectric coupling effect,the current will increase by 3 orders of magnitude under the action of magnetic field,indicating the sensitivity of the magnetic field detector.The transfer method proposed in this paper can be applied to the transfer of other different materials.Recent advances in thin-film deposition technique such as pulsed laser deposition?PLD?makes it possible to epitaxially combine different materials with atomic level accuracy as quasi-two dimensional heterostructures.However,due to lattice mismatch and elevated growth temperature,it is not trivial to grow high quality oxides directly onto substrates such as PET,PDMS,Mica and so on.So that,it remains challenging to get flexible heterostructured oxide thin films.The transfer method in the paper makes it possible to obtain flexible heterostructured oxide thin films.This is of great significance for basic research of the functional oxide and the application of flexible electronic devices.