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Structural color based on Fabry–Perot (F-P) cavity enables a wide color gamut with high resolution at submicroscopic scale by varying its geometrical parameters. The ability to design such parameters that can accurately display the desired color is therefore crucial to the manufacturing of F-P cavities for practical applications. This work reports the first inverse design of F-P cavity structure using deep learning through a bidirectional artificial neural network. It enables the production of a significantly wider coverage of color space that is over 215% of sRGB with extremely high accuracy, represented by an average Δ E 2000 value below 1.2. The superior performance of this structural color-based neural network is directly ascribed to the definition of loss function in the uniform CIE 1976-Lab color space. Over 100,000 times improvement in the design efficiency has been demonstrated by comparing the neural network to the metaheuristic optimization technique using an evolutionary algorithm when designing the famous painting of “Haystacks, end of Summer” by Claude Monet. Our results demonstrate that, with the correct selection of loss function, deep learning can be very powerful to achieve extremely accurate design of nanostructured color filters with very high efficiency.

Poly(N-isopropylacrylamide) (PNIPAm) is widely used to fabricate cell sheet surfaces for cell culturing, however copolymer and interpenetrated polymer networks based on PNIPAm have been rarely explored in the context of tissue engineering. Many complex and expensive techniques have been employed to produce PNIPAm-based films for cell culturing. Among them, spin coating has demonstrated to be a rapid fabrication process of thin layers with high reproducibility and uniformity. In this study, we introduce an innovative approach to produce anchored smart thin films both thermo- and electro-responsive, with the aim to integrate them in electronic devices and better control or mimic different environments for cells in vitro. Thin films were obtained by spin coating of colloidal solutions made by PNIPAm and PAAc nanogels. Anchoring the films to the substrates was obtained through heat treatment in the presence of dithiol molecules. From analyses carried out with AFM and XPS, the final samples exhibited a flat morphology and high stability to water washing. Viability tests with cells were finally carried out to demonstrate that this approach may represent a promising route to integrate those hydrogels films in electronic platforms for cell culture applications.

The inherently rapid ligand substitution kinetics associated with the novel and chemically compatible precursors, [MCl3(EnBu2)3] (M = Sb, Bi; E = Se, Te), enable CVD growth of ternary Bi2(Se1-xTex)3 and (Bi1-ySby)2Te3 thin films with very good compositional, structural and morphological control, for the first time. X-ray diffraction data follow Vegard’s law and Raman bands shift linearly with the atom substitutions, indicating very well-distributed solid solutions.

This paper presents a method for the electrodeposition of stoichiometric, crystalline HgTe, which provides advantages over conventional HgTe preparation techniques, such as physical and chemical vapor deposition, in a number of ways; e.g. fast deposition rates (2 mm/hr) and the ability to reliably produce stoichiometric or near-stoichiometric material. The HgTe is prepared in a dichloromethane based plating bath using [NnBu4]2[TeCl6] and [NnBu4]2[HgCl4] as the precursors for Te and Hg, respectively. The paper details the electrochemical behavior of the plating bath and its components, together with a detailed characterization of the morphology, crystallinity and composition of the prepared HgTe.

Thermoelectric generators are attractive for autonomous sensor systems where regular battery replacement would not only cause an increase in the maintenance costs and discontinuity in the operation, but also destroy the concept of a truly autonomous system. Micro-thermoelectric generators utilise thin films of material for energy harvesting which can greatly reduce the amount of material used, which is especially important for rare elements such as tellurium. Thin films of Bi2Te3 were successfully prepared via a single source precursor CVD method. The thermoelectric performance of these films is improved by alloying a Bi2Se3 precursor to deposit ternary Bi2Te3-xSex. The composition of the ternary system is tuned to optimise the combination of carrier concentration and mobility to give a three-fold enhancement of the thermoelectric power factor at 300 K, and six-fold enhancement at 500 K, with respect to Bi2Te3. This improvement from the substitution of Te with Se is believed to be due to donor effects, as well as point defects caused by this substitution.

Undoped ZnO thin films with tunable electrical properties have been achieved by adjusting the O2 plasma time in the plasma enhanced atomic layer deposition process. The structural, compositional and electrical properties of the deposited ZnO films were investigated by various characterization techniques. By tuning the plasma exposure from 2 to 8s, both resistivities and carrier concentrations of the resultant ZnO films can be modulated by up to 3 orders of magnitude. Forming-free TiN/ZnO/TiN resistive memory devices have been achieved by choosing the ZnO film with the plasma exposure time of 6s. This deposition method offers a great potential for producing other un-doped metal oxides with tunable properties as well as complex multilayer structures in a single deposition. Display Omitted

We have recently reported a new method for the electrodeposition of thin film and nanostructured phase change memory (PCM) devices from a single, highly tuneable, non-aqueous electrolyte. The quality of the material was confirmed by phase cycling via electrical pulsed switching of both 100 nm nano-cells and thin film devices. This method potentially allows deposition into extremely small confined cells down to less than 5 nm, 3D lay-outs that require non-line-of-sight techniques, and seamless integration of selector devices. As electrodeposition requires a conducting substrate, the key condition for electronic applications based on this method is the use of patterned metal lines as the working electrode during the electrodeposition process. In this paper, we show the design and fabrication of a 2D passive memory matrix in which the word lines act as the working electrode and nucleation site for the growth of confined cells of Ge–Sb–Te. We will discuss the precursor requirement for deposition from non-aqueous, weakly coordinating solvents, show the transmission electron microscopy analysis of the electrodeposition growth process and elemental distribution in the deposits, and show the fabrication and characterisation of the Ge–Sb–Te memory matrix.

We report on the fabrication of memory devices based on a nanoporous GeSbTe layer electrodeposited inbetween TiN and Ag electrodes. It is shown that devices can operate along two distinct electrical modes consisting of a volatile or a non-volatile resistance switching mode upon appropriate preconditioning procedures. Based on electrical measurements conducted in both switching modes and physical analysis performed on a device after electrical stress, resistance switching is attributed to the formation/dissolution of a conductive filament from the Ag electrode into the GST layer whereas the volatile/non-volatile resistance switching is attributed to the presence of an interface layer between the GST and the Ag top electrode. Due to their simple, low-cost and low-temperature fabrication procedure, these devices could be advantageously exploited in flexible electronic applications or embedded into the back-end of line CMOS technology.

Cu/amorphous-SiC (a-SiC) electrochemical metallization memory cells have been fabricated with two different counter electrode (CE) materials, W and Au, in order to investigate the role of CEs in a non-oxide semiconductor switching matrix. In positive bipolar regime with Cu filaments forming and rupturing, the CE influences the OFF state resistance and minimum current compliance. Nevertheless, a similarity in SET kinetics is seen for both CEs, which differs from previously published SiO2 memories, confirming that CE effects are dependent on the switching layer material or type. Both a-SiC memories are able to switch in the negative bipolar regime, indicating Au and W filaments. This confirms that CEs can play an active role in a non-oxide semiconducting switching matrix, such as a-SiC. By comparing both Au and W CEs, this work shows that W is superior in terms of a higher ROFF/RON ratio, along with the ability to switch at lower current compliances making it a favourable material for future low energy applications. With its CMOS compatibility, a-SiC/W is an excellent choice for future resistive memory applications.

Amorphous SiC with embedded Cu nanoparticles (a-SiC:Cu) was investigated as the insulator layer of Cu/a-SiC:Cu/Au resistive memory. The effect of the Cu embedding on resistive switching characteristics was studied for 20 and 30 vol% Cu. Reduced forming and SET voltages and increased endurance was observed for devices with 30Cu%. At the same time, all key advantageous characteristics of amorphous SiC resistive memory such as ON/OFF ratio of 107 and the co-existence of bipolar and unipolar modes were maintained upon Cu embedding. All above suggests that Cu embedding could be considered as a promising method to improve the overall performance of Cu/a-SiC:Cu/Au resistive memories.

The neutral, distorted octahedral complex [TiCl4(Se n Bu2)2] (1), prepared from the reaction of TiCl4 with the neutral Se n Bu2 in a 1:2 ratio and characterized by IR and multinuclear (1H, 13C{1H}, 77Se{1H}) NMR spectroscopy and microanalysis, serves as an efficient single-source precursor for low-pressure chemical vapor deposition (LPCVD) of titanium diselenide, TiSe2, films onto SiO2 and TiN substrates. X-ray diffraction patterns on the deposited films are consistent with single-phase, hexagonal 1T-TiSe2 (P3m1), with evidence of some preferred orientation of the crystallites in thicker films. The composition and structural morphology was confirmed by scanning electron microscopy (SEM), energy dispersive X-ray, and Raman spectroscopy. SEM imaging shows hexagonal plate crystallites growing perpendicular to the substrate, but these tend to align parallel to the surface when the quantity of reagent is reduced. The resistivity of the crystalline TiSe2 films is 3.36 ± 0.05 × 10-3 Ω·cm with a carrier density of 1 × 1022 cm-3. Very highly selective film growth from the reagent was observed onto photolithographically patterned substrates, with film growth strongly preferred onto the conducting TiN surfaces of SiO2/TiN patterned substrates. TiSe2 is selectively deposited within the smallest 2 μm diameter TiN holes of the patterned TiN/SiO2 substrates. The variation in crystallite size with different diameter holes is determined by microfocus X-ray diffraction and SEM, revealing that the dimensions increase with the hole size, but that the thickness of the crystals stops increasing above ∼20 μm hole size, whereas their lengths/widths continue to increase.

Resistive switching of W/amorphous (a)-SiOxCy:H/Cu resistive memories incorporating solely native back-end-of-line (BEOL) materials were studied. A-SiC1.1:H, a-SiO0.9C0.7:H, and a-SiO1.5C0.2:H were exploited as switching layers for resistive memories which all show resistive-switching characteristics with ultrahigh ON/OFF ratios in the range of 106 to 1010. Ohmic conduction in the low resistance state is attributed to the formation of Cu conductive filament inside the a-SiOxCy:H switching layer. Rupture of the conductive filament leads to current conduction dominated by Schottky emission through a-SiOxCy:H Schottky contacts. Comparison of the switching characteristics suggests composition of the a-SiOxCy:H has influences on VFORM and VSET, and current conduction mechanisms. These results demonstrate the capability to achieve functional W/a-SiOxCy:H/Cu using entirely BEOL native materials for future embedded resistive memories.Resistive switching of W/amorphous (a)-SiOxCy:H/Cu resistive memories incorporating solely native back-end-of-line (BEOL) materials were studied. A-SiC1.1:H, a-SiO0.9C0.7:H, and a-SiO1.5C0.2:H were exploited as switching layers for resistive memories which all show resistive-switching characteristics with ultrahigh ON/OFF ratios in the range of 106 to 1010. Ohmic conduction in the low resistance state is attributed to the formation of Cu conductive filament inside the a-SiOxCy:H switching layer. Rupture of the conductive filament leads to current conduction dominated by Schottky emission through a-SiOxCy:H Schottky contacts. Comparison of the switching characteristics suggests composition of the a-SiOxCy:H has influences on VFORM and VSET, and current conduction mechanisms. These results demonstrate the capability to achieve functional W/a-SiOxCy:H/Cu using entirely BEOL native materials for future embedded resistive memories.

We report the properties of a series of electrodeposited Ge-Sb-Te alloys with various compositions. It is shown that the Sb/Ge ratio can be varied in a controlled way by changing the electrodeposition potential. This method opens up the prospect of depositing Ge-Sb-Te super-lattice structures by electrodeposition. Material and electrical characteristics of various compositions have been investigated in detail, showing up to three orders of magnitude resistance ratio between the amorphous and crystalline states and endurance up to 1000 cycles.

We report here a ZrO2−x /ZrO2-based bilayer resistive switching memory with unique properties that enables the selection of the switching mode by applying different electroforming current compliances. Two opposite polarity modes, positive bipolar and negative bipolar, correspond to the switching in the ZrO2 and ZrO2−x layer, respectively. The ZrO2 layer is proved to be responsible for the negative bipolar mode which is also observed in a ZrO2 single layer device. The oxygen deficient ZrO2−x layer plays the dominant role in the positive bipolar mode, which is exclusive to the bilayer memory. A systematic investigation of the ZrO2−x composition in the bilayer memory suggests that ZrO1.8 layer demonstrates optimum switching performance with low switching voltage, narrow switching voltage distribution and good cycling endurance. An excess of oxygen vacancies, beyond this composition, leads to a deterioration of switching properties. The formation and dissolution of the oxygen vacancy filament model has been proposed to explain both polarity switching behaviours and the improved properties in the bilayer positive bipolar mode are attributed to the confined oxygen vacancy filament size within the ZrO2−x layer.