TECHNICAL FIELD

[0001] The present invention generally relates to electronics and optoelectronics, and more particularly relates to a reconfigurable solid-state optoelectronic framework based on a dynamic layer architecture.

BACKGROUND OF THE DISCLOSURE

[0002] Thin-film architectures are a staple in a wide range of technologies such as semiconductor devices, optical coatings, magnetic recording, solar cells and batteries. But, despite the industrial success of thin-film technology mostly due to easy fabrication and low cost, a fundamental drawback remains: it is challenging to alter the features of the film once fabricated (i.e., physically tuneable thin-film structure on demand continues to elude). After the initial design and deposition of thin-film devices, the structures are fixed and exhibit properties confined to their structure and configuration. [0003] Significant effort has been devoted to developing tuneable artificial architectures from material science and structure engineering. Active soft and solid materials have provided the ability to modify micro -structures via external stimulation such as a solvent environment, mechanical stress or magnetic, electrical, thermal or optical treatment. Structures based on soft materials are fabricated via direct chemical or self-assembly methods, for example by digital light printing or assistant templates, which allows easy realization of different dimensional structures. In contrast, however, solid materials are preferred to achieve high resolution nanostructures for colour generation beyond the limitations of the current display and colour printing technologies realized though redox reactions and phase transformation of materials. In addition, laser printing technologies are designed to reshape the fabricated metallic nanostructures for dynamic colour printing.

[0004] Yet, structure responses of a single deposited solid-state device are limited and cannot yield dynamic structure alteration because these responsive nanostructures are typically complex and non-conformable. In addition, conventional techniques to achieve multiple properties still utilize sub-pixels of varying thicknesses with complex device structures and specific coding strategies.

[0005] The increasing demand for dynamic color tuning for emerging applications such as displays, wearable optoelectronic devices, sensors, data storage and augmented reality devices has driven the development of advanced dynamic, low power and high- resolution color tuning technologies. However, despite significant efforts made in material and engineering innovations and continuous efforts in advancing innovative color modulation with widespread applications, developing practical technologies capable of dynamically and reversibly fine-tuning a wider gamut color in the visible range remains challenging. Currently, most color modulation techniques rely on blending and encoding three basic colors, red-green-blue (RGB), which requires specific encoding pixels, complex structure design and unremitting energy.

[0006] Thus, there is a need for fabrication techniques and device architecture of photonic nanostructures which can be dynamically adjusted after fabrication in a facile manner. In addition, fabrication techniques for such photonic nanostructure are desired which provide simplified, less-extensive, low-cost processes. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure. SUMMARY

[0007] According to at least one aspect of the present embodiments, a dynamically reconfigurable thin-film structure for solid-state devices is provided. The device includes a bottom electrode, a top electrode layer and a functional layer sandwiched between the top electrode layer and the bottom electrode layer. The functional layer includes a first layer of mobile highly reflective elements and a second layer of amorphous or mesoporous dielectric materials.

[0008] According to another aspect of the present embodiments, a method for color modulation of a dynamically reconfigurable color-tuneable thin-film structure solid- state device is provided. The device includes a bottom electrode, a top electrode and a functional layer sandwiched between the top electrode and the bottom electrode, wherein the functional layer comprises a first layer of mobile highly reflective elements and a second layer of amorphous or mesoporous material. The method includes providing for a first predetermined time duration a first bottom electrode voltage to the bottom electrode which is positive as compared to a first top electrode voltage simultaneously applied to the top electrode to tune a viewable color of at least a portion of the top electrode from a first color to a second color.

[0009] And according to a further aspect of the present embodiments, a method for fabrication of a dynamically reconfigurable color-tuneable device is provided. The method includes providing a substrate, depositing a bottom electrode layer on the substrate, and depositing a lower functional layer on the bottom electrode layer, the lower functional layer including mobile highly reflective elements. The method also includes depositing an upper functional layer on the lower functional layer, the upper functional layer including amorphous or mesoporous material, and depositing a top electrode layer on the upper functional layer. The top electrode layer includes a transparent electrode material. The upper functional layer is deposited to a predetermined thickness and an initial viewable color of the at least a portion of the dynamically reconfigurable color-tuneable device is determined by the predetermined thickness to which the upper functional layer is deposited.

BRIEF DESCRIPTION OF THE DRAWINGS [0010] The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to illustrate various embodiments and to explain various principles and advantages in accordance with present embodiments.

[0011] FIG. 1, comprising FIGs. 1A and IB depicts microscopic images of a floating solid-state thin film (FSTF) in accordance with the present embodiments, wherein FIG. 1A depicts SEM images and high-resolution transmission electron microscope (HRTEM) images of the cross-section of the as-deposited sample and a schematic vertical structure diagram, including the amorphous Fe ₂ O ₃ and crystal Ag layers and FIG. IB depicts a HRTEM image of the interface of functional layers under an electrical field.

[0012] FIG. 2 depicts a schematic illustration of the tuneable reconfigurable property of the FSTF in accordance with the present embodiments.

[0013] FIG. 3, comprising FIGs. 3 A to 3C, depicts scanning transmission electron microscope (STEM) images and corresponding energy dispersive X-ray (EDX) mappings of three key elements (Fe, O and Ag) of a typical FSTF device in accordance with the present embodiments at three different states, wherein FIG. 3A depicts an initial state, FIG. 3B depicts a partially activated state and FIG. 3C depicts a fully activated state.

[0014] FIG. 4, comprising FIGs. 4A and 4B, depicts reversible and dynamic multicolour tuning of a FSTF-based solid-state photonic device under positive bias in accordance with the present embodiments, wherein FIG. 4A is a schematic illustration of a setup of application of the positive bias to the device and FIG. 4B is a graph of a measured time-resolved reflectance spectra of the FSTF device.

[0015] FIG. 5, comprising FIGs. 5A and 5B, depicts reversible and dynamic multicolour tuning of a FSTF-based solid state photonic device under negative bias in accordance with the present embodiments, wherein FIG. 5A is a schematic illustration of a setup of application of the negative bias to the device and FIG. 5B is a graph of a measured time-resolved reflectance spectra of the FSTF device.

[0016] FIG. 6, comprising FIGs. 6A to 6C, depicts graphs of EDX line scans of the three key elements (Fe, O and Ag) of the dynamic reversible FSTF architecture reconfiguration in accordance with the present embodiments, wherein FIG. 6 A depicts the EDX line profile spectra of the Fe, O and Ag distribution across the floating stack architecture when the FSTF device is in a partially activated state, FIG. 6B depicts the EDX line profile spectra of the Fe, O and Ag distribution across the floating stack architecture when the FSTF device is in a fully activated state, and FIG. 6C depicts the EDX line profile spectra of the Fe, O and Ag distribution across the floating stack architecture in the reversible treated FSTF device.

[0017] FIG. 7, comprising FIGs. 7A to 7F, depicts electric induced color change in a nano-pixelated pattern on a FSTF in accordance with the present embodiments, wherein FIG. 7A is a schematic illustration of the electric induced colour change of the thin film device by conductive atomic force microscope (CAFM), FIG. 7B is a microscope image of four inscribed letters in the nano-pixelated pattern, FIG. 7C is a current mapping in the letter “S” at a first tip bias, FIG. 7D is a current mapping in the letter “U” at a second tip bias, FIG. 7E is a current mapping in the letter “T” at a third tip bias, and FIG. 7F is a current mapping in the letter “D” at a fourth tip bias.

[0018] And FIG. 8 depicts a large-scale color image of a colorful Merlion image printed on a FSTF by controlling the thickness of crystal Fe203 layer using a shadow mask in accordance with the present embodiments.

[0019] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been depicted to scale.

DETAILED DESCRIPTION

[0020] The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. It is the intent of present embodiments to present dynamically reconfigurable thin-film-based functional devices and methods for their fabrication. A solid-state framework with a reconfigurable dynamic layer architecture (DLA) in accordance with present embodiments provides a new color-tuning technology for wide applications, such as displays, smart glass, energy efficient windows, color-printing, sensors and other visualization applications. In addition, the DLA framework in accordance with the present embodiments enables tuneable structure design for functional devices without requiring a more cumbersome fabrication process.

[0021] The novel reconfigurable dynamic layer architecture (DLA) in accordance with the present embodiments advantageously provides color-tuning technologies within a broad wavelength range in the visible wavelengths. The reconfigurable DLA in accordance with the present embodiments includes a core multilayer structure including a bottom electrode, a functional layer, and a transparent top electrode, where the functional layer consists of a bottom highly mobile elements (silver (Ag), copper (Cu) or other similar mobile metals) thin film and a top amorphous or mesoporous thin dielectric film 130. In accordance with the present embodiments, an atomic movement solid-state display (AMSD) via the novel dynamic layer architecture (DLA) was demonstrated which realized dynamic reversible multicolor fine-tuning over the visible light range in a single device. The DLA structure uses stable inorganic thin film materials such as metal oxides, sulfides, chalcogenide materials (such as Ge-Te, Ge-Sb- Te (GST), Ge-Se, Ge-Sb-Sb) and other materials with channels or space as the function layer and silver or copper or other similar mobile metal elements as the mobile metal layer. The color originates from the movement of mobile metal elements (e.g., silver) from the bottom layer to the insulator layer, whereby the optical properties, such as reflectivity of the multiple stack of the thin-film stack structure are tuned due to the movement of mobile metal elements. This novel type of display which enables color tuning by controlling the movement of the atoms of the metal layer inside the function layer is termed an atomic movement solid-sate display (AMSD). The DLAs can display the basic color components such as red, green and blue (RGB) and advantageously achieve fine modulation of color in devices and large films. The color of the display can be modulated by the thicknesses of the function layer and the bottom layer, which can vary from several nanometers to hundreds of nanometers.

[0022] The color can advantageously be dynamically fine-modulated by applying various external energies, such as thermal heat, electrical voltage, or other external energies. More importantly, the color-modulation of the AMSD is polarity-dependent and reversible by switching the polarization of the applied external energy, such as by switching the polarization of a voltage bias, on a single device. Further, the proposed DLA reconfigurable structure in accordance with the present embodiments enables a general framework not only for reflective displays, micro displays, optical components, smart glass, environment-friendly windows, security marks, color-printing and other visualization applications, but also for smart device design without a cumbersome fabrication process.

[0023] In addition to such devices, a methodology to modify the thickness and sequence of the innermost solid-state thin film layers in accordance with the present embodiments is proposed. In one embodiment, a thin film stack of amorphous iron oxide and silver is fabricated and, by applying a suitable voltage bias and then reversing such bias, the silver layer can be floated above or below the oxide layer by virtue of the migration of silver atoms. Scanning transmission electron microscope (STEM) reveals various sequences and thicknesses of the silver/oxide layers achieved through different experimental conditions and, as a proof-of-principle, a dynamic change of structural colour of the stack derived from this process is shown.

[0024] The novel atom movement solid-sate display (AMSD) via DLA in accordance with the present embodiments is based on a simple thin-film sandwich stmctureln accordance with the present embodiments, all thin-film layers are deposited sequentially by using standard semiconductor deposition techniques, such as physical vapor deposition, chemical vapor deposition or other deposition techniques.

[0025] Referring to FIGs. 1A and IB, images 110, 120, 135, 140, 145 (FIG. 1A) and image 150 (FIG. IB) depict microscopic images of a floating solid-state thin film (FSTF) device fabricated in accordance with the present embodiments. The FSTF device showed multiple optical responses encompassing multicolours for a single photonic device. High-mobility and reflective silver (Ag) and amorphous ferric oxide (Fe ₂ O ₃ ) were used as key functional layers of the FSTF device. After fabrication, the FSTF device could be dynamically reconfigured under electrical stimulus, reconfiguring parameters of the FSTF device such as layer number, thickness and order.

[0026] The image 110 depicts a scanning electron microscope (SEM) image of the cross-section of the as-deposited FSTF, wherein the image 120 depicts a schematic illustration of a vertical structure diagram including a substrate layer 122, a bottom electrode (BE) layer 124 of a tungsten-titanium alloy (TiW), and a transparent top electrode (TE) layer 126 of indium tin oxide (ITO), where the TE layer 126 and the BE layer 124 sandwich a functional bi-layer including mobile metal elements 128 of silver (Ag) and rich-defect materials 130 such as ferric oxide (Fe ₂ O ₃ ). In the SEM image 110 where the scale bar 132 is one micrometer, the thicknesses of the layers of the FSTF depicted are as follows: the TE layer 126 of ITO is 45 nm, the layer 130 of Fe ₂ O ₃ is 100 nm, the layer 128 of Ag is 140 nm and the BE layer 124 of TiW is 70 nm. A high- resolution transmission electron microscope (HRTEM) image 135 depicts the interface of functional layers 128, 130 (i.e., Ag and Fe203) where the scale bar 137 for the HRTEM image 135 is five nanometers. The HRTEM images 140, 145 depict amorphous Fe ₂ O ₃ and crystal Ag layers, respectively with scale bars 142, 147 of ten nanometers.

[0027] Scanning transmission electron microscope (STEM) observation directly revealed that the in- situ layer reconfiguration is triggered by atomic movement of silver through the heterolayers stack driven by an electric field as shown in the HRTEM image 150. The HRTEM image 150 depicts the functional layers 128, 130 of the FSTF device under an electrical field 160 of one volt for fifty seconds whereby the Ag 128 is mobile through the amorphous Fe ₂ O ₃ forming layers 170 of Fe ₂ O ₃ -Ag. This evidences that both micrometer-sized (50 mih, each pixel) and nano-pixelated (100 nm, each pixel) multicolour fine-tuning are both advantageously achievable in a single FSTF-based optoelectronic device, enabling considerable progress in large panel and high-resolution structural colour and eliminating the need to blend and encode RGB pixels. Moreover, FSTF-based photonic devices in accordance with the present embodiments do not require a constant energy supply to retain the colours, allowing for potential outdoor eco-environmental usage.

[0028] The disordered state depicted in the image 150 provides more channels for Ag-i- movement under electrical fields, while just a little Ag 128 can pass through the crystal Fe ₂ O ₃ layer. Ab initio molecular dynamics (AIMD) calculations found that there is little space for Ag movement in the crystal Fe ₂ O ₃ . With AG and Fe ₂ O ₃ as the lower and upper functional layers, respectively, the Ag layer is the key to the tuneable optic properties of the FSTF due to the high mobility and reflectivity of the Ag. Under an electrical field (e.g., the electrical field 160), the mobile Ag 128 can move into the amorphous Fe ₂ O ₃ layer 130 and pass through this layer, evidenced by HRTEM image 150. A clear aggregation layer of Ag atoms 128 can be found among the amorphous Fe ₂ O ₃ as shown by the lines 180.

[0029] Based on the above characterization results, the working principle of the dynamically reconfigurable DLA of the FSTF in accordance with the present embodiments is schematically illustrated in FIG. 2. The basic structure is depicted in a first illustration 210 where the Ag layer 128 is between the bottom electrode 124 and the Fe ₂ O ₃ dielectric layer 130. Under a positive electrical field in a second illustration 220 provided by a voltage source 222, the silver is ionized and the silver ions (Ag ⁺ ) move up and pass through the Fe ₂ O ₃ layers. After additional application of the electric field as shown in a third illustration 230, the Ag assembles between the top electrode 126 and the Fe ₂ O ₃ dielectric layer. Once an opposite electric field is applied, the silver ions move back below the Fe ₂ O ₃ layer in accordance with the present embodiments. [0030] For the as-deposited FSTF device, the configuration of the heterolayer stack is consistent with the intended design with clear layer interfaces as shown in the SEM image 110 (FIG. 1 A), which is due to negligible thermal diffusion between Ag and Fe ₂ O ₃ at room temperature. When a positive bias is applied to the bottom electrode, Ag atoms are ionized (Ag → e- 83 + Ag ⁺ ), forming highly mobile Ag+ ions at the Ag/ Fe ₂ O ₃ interface. Under an electric field, Ag-i- ions are driven into the Fe ₂ O ₃ layer to form Ag- Fe ₂ O ₃ hybrids, which leads to thickening of the Fe ₂ O ₃ layer as shown in the illustration 220 (FIG. 2). With continuous injection of Ag-i- ions, the excess ions (Ag+) are continuously driven through the Ag-Fe ₂ O ₃ hybrids and recombined with electrons at the anode (GGO/ Fe ₂ O ₃ interface). A new silver layer is formed underneath the top ITO electrode due to the continuous reduction of Ag-i- (Ag-i- + e- → Ag) as shown in the illustration 230. When the bias time is prolonged, the newly formed Ag layer expands and “pushes” the underlayer (Fe ₂ O ₃ ) downwards, resulting in dynamic reconfiguration of the multilayer structure. When the polarity of bias voltage is reversed, a similar dynamic reconfiguration process occurs but starts from the side of the accumulated Ag layer under the GGO. Such inverse dynamic reconfiguration mirrors the process under the positive bias and eventually causes the sample returning to its initial state.

[0031] To gain insights into the underlying mechanism of the dynamic multicolour tunability from direct experimental results, STEM and energy dispersive X-ray (EDX) analysis of the FSTF devices were performed. As shown in FIGs. 3A, 3B and 3C, three FSTF devices with distinct colours (orange 300, deep purple 330, green 360) were analyzed, each of which was generated at 0, 50 and 200 seconds at +1 V bias, respectively, representing an initial stage as depicted in the illustration 300, a partially activated state as depicted in the illustration 330 and a saturated or fully activated state as depicted in the illustration 360. The saturated state refers to a state in which no obvious colour change occurs even as the bias voltage is provided for a longer bias time. The heterolayer structure of the initial state can be clearly identified from the STEM image 305 and the interface between each layer can be verified by the EDX elemental (Ag, Fe, O) mappings 310, 315, 320.

[0032] Interestingly, for the partially activated sample 330, FSTF reconfiguration can be observed from the STEM image 335 and the EDX elemental mappings 340, 345, 350. Unlike the initial state, the bottom Ag layer becomes significantly thinner from the original 140 nm to -100 nm, and the Fe ₂ O ₃ layer expands accordingly. According to conventional literature in the art, increase in the thickness of thin films doped with Ag is mainly attributed to the variation of lattice strain, the particle size and agglomeration. The average size of particles in Fe ₂ O ₃ would be enhanced with Ag incorporation, resulting in the expansion of the Fe ₂ O ₃ layer. The EDX elemental mappings 340, 345, 350 reveal that Ag has migrated into the Fe ₂ O ₃ layer driven by the electric field and becomes almost uniformly distributed in the Fe ₂ O ₃ layer. The Ag-Fe ₂ O ₃ hybrids will reach a saturation point (around 18 at. %), based on the EDX line profile of Ag. Moreover, an additional Ag layer has appeared between the Fe ₂ O ₃ layer and the GGO electrode, evidencing that some Ag has passed through the Fe ₂ O ₃ layer and accumulated under the top electrode. This means that a floating multilayer film can be attained in a controlled electric field.

[0033] If a saturated device is biased long enough, the bottom Ag layer almost disappears while the Ag layer on top of the Fe ₂ O ₃ layer has expanded substantially to -60 nm as shown in the STEM image 365, suggesting that more Ag has been driven out of the bottom Ag layer, passed through the Fe ₂ O ₃ layer, and accumulated under the top electrode. When Ag reaches saturation in the Fe ₂ O ₃ layer, Ag atoms continuously precipitate from the Fe ₂ O ₃ layer and form a new layer underneath the top electrode, resulting in a change of heterolayer sequence, number of layers and layer thicknesses within the FSTF. Such STEM observation of the direct-assembled reconfiguration of multilayer stacks further corroborates the working principles of the FSTF as shown in the illustrations 210, 220, 230 (FIG. 2).

[0034] X-ray photoelectron spectroscopy (XPS) was employed to analyze the Fe203 layer of the three samples (pristine 300, partly activated 330, and fully activated 360) to extract information on the chemical states. By applying a simplified method for fitting Fe2p spectra, all three Fe2p high-resolution spectra of the initial device 300, the partially activated device 330 and the saturated device 360 showed two Fe2p _3/2 components at 712.9 eV and 710.9 eV. The lower binding energy position of Fe2p _3/2 is within the reported range of Fe203. Furthermore, the 8.3 eV separation between the satellite and Fe2p _3/2 provides additional evidence that Fe203 does not undergo change chemically upon colour change. [0035] A FSTF-based solid state photonic device was fabricated in accordance with the present embodiments to further explore time-resolved tunability. Referring to FIG. 4A, a schematic illustration 400 depicts application of a positive bias by an applied voltage 410 of one volt to the FSTF-based solid state photonic device 420 in accordance with the present embodiment to manifest the bias-time-controlled tunability. The device comprises layers of ITO (45 nm )/ Fe ₂ O ₃ (100 nm )/ Ag (140 nm )/ TiW (70 nm) and a positive bias is defined as when a positive voltage is applied to the bottom TiW electrode as shown in the illustration 400. Referring to FIG. 4B, a graph 430 depicts measured time-resolved reflectance spectra of the FSTF device under the positive bias. The time- resolved visible spectra under one-volt positive bias was recorded for 200 seconds. The maximum intensity of red peak (~640 nm) significantly decreases 432, 434, 436, 438, 440 while the blue peak (~450 nm) increases 442, 444, 446 during the measurement period, resulting in a clear colour change.

[0036] We further study the reversible optical-tuning ability of FSTF-based photonic device by reversing the polarity of the electric field. Referring to FIG. 5A, a schematic illustration 500 depicts application of the negative bias by an applied voltage 510 of - 1.3 volt to the FSTF-based solid state photonic device 520 in accordance with the present embodiment to manifest the reverse bias-time-controlled tunability. Referring to FIG. 5B, a graph 530 depicts measured time-resolved reflectance spectra of the FSTF device under the negative bias. When the negative bias of -1.3 V is applied to the bottom electrode, the time-resolved reflectance spectra shows a red-shift of the maximum reflectance peak from blue 532, 534 to purple 536, 538 to red 540, 542. It is noteworthy that the colour changes from blue 532, 534 and deep purple 536, 538 and red 540, and finally to the colour 542 of the as-deposited state, show a mirrored response to the positive bias operation.

[0037] For further investigation of colour-change with dynamic reversible FSTF architecture reconfiguration, EDX line scan was performed to understand the elemental distribution on the three FSTF devices with typical colour (partially activated, fully activated and reversed devices). Referring to FIGs. 6A, 6B and 6C, graphs 600, 630, 660 depict EDX line profile spectra of the three key elements (Fe, O and Ag) of the dynamic reversible FSTF architecture reconfiguration in accordance with the present embodiments in a partially activated state (the graph 600), a fully activated state (the graph 630), and a reversible state (the graph 660). The EDX line scan profile of the partially activated device in the graph 600 indicates the floating architecture behaviour in the starting period when Ag moves into the amorphous Fe203 layer, which is consistent with the overall structure altering in FIG. 3B. Meanwhile, the graph 630 displays the key elements (Ag, Fe and O) distribution of a device fully activated. To understand the elemental distribution on the reversible device, an EDX line scan was performed on a FSTF device in accordance with the present embodiments under application of -1.3 V for three hundred seconds as shown in the graph 660. The graph 660 reveals that the top Ag atoms pass through the Fe ₂ O ₃ layer and almost revert back to the bottom position, indicating a similar structure as the pristine device in the graph 600. The reversible architecture also can be confirmed by TEM images of the vertical structure, which evidence that the majority of Ag move back to the pristine position below the Fe ₂ O ₃ layer.

[0038] Conductive atomic force microscope (CAFM) has been effectively used to mimic nano-pixel imaging and reflective display. To explore the high-resolution ability of FSTF, CAFM was employed to pattern four letters (S, U, T and D) on a FSTF thin film stack 702 in accordance with the present embodiments as shown in the schematic illustration 700 in FIG. 7A. A nano-size conductive tip (~100 nm) 704 is placed on the top electrode 706 surface of the FSTF device 702 and negatively biased. The layers of the FSTF device are the transparent top electrode 706, the amorphous Fe203 layer 707, the Ag layer 708 and the TiW bottom electrode 709. The thicknesses of the layers are a 50 nm thickness of the bottom electrode layer 709, a 140 nm thickness of the Ag layer 708 and a 25 nm thickness of the Fe203 layer 707.

[0039] FIG. 7B depicts a microscope image 710 of the four inscribed letters in the nano-pixelated pattern. When the voltage goes beyond -4 V, as observed under the microscope view 710, patterns with substantial colour contrasts are generated. The colour changes from the initial yellow to orange (-4 V), blue (-6 V) and green (-8 V). Voltages of -4, -5, -7 and -8 V were applied to write the letters “S”, “U”, “T”, “D” upon the same piece of FSTF. The patterned areas were fixed at 50 x 50 pm ² with 512 x 256 pixels. The unpolarized optical microscope image 710 presents significant colour contrast, showcasing the feasibility of nano-pixeled colour modulation of the FSTF device 702 in accordance with the present embodiments. Subsequently, each letter is scanned using a very low bias (0.5 V) to obtain reliable current mapping information; this low bias scanning voltage is sufficiently low to not trigger colour change in accordance with the present embodiments. In current maps 720 (FIG. 9C), 730 (FIG. 9D), 740 (FIG. 9E), 750 (FIG. 9F), colour-changed regions produce much higher currents than the pristine regions, which marks a difference in resistance between the discoloured and non-discoloured regions. This also explains the current increase in the colour-changed regions measured by CAFM owing to the incorporation of highly conductive Ag.

[0040] It is noted that the colour will change with variation of the material index. The ability of colour-tuning by adopting crystal Fe203 with various thickness in accordance with the present embodiments allows the colours of printed images with same structure to be different, due to variations in the amorphous Fe ₂ O ₃ . Referring to FIG. 8, a photograph 800 depicts a bright Merlion image using crystal Fe ₂ O ₃ deposited on a silicon wafer using a shadow mask to control the amorphous deposition thickness where the top of the merlion image and the “N” and “G” of Singapore have a Fe ₂ O ₃ layer thickness of 70 nm, the middle of the merlion image has a 120 nm Fe ₂ O ₃ layer thickness, the bottom of the merlion image and a left half of the “O” have a 50 nm Fe ₂ O ₃ layer thickness, the “S” and the “I” have a 100 nm Fe ₂ O ₃ layer thickness, a right half of the “O”, the “R” and the Έ” have a 60 nm Fe ₂ O ₃ layer thickness, the “A” has a 80 nm Fe ₂ O ₃ layer thickness, and the “P” has a 110 nm Fe ₂ O ₃ layer thickness.

Thus, it can be seen that the present embodiments provide a viable and scalable approach for tuneable modern devices with nanometer precision on large area hard/stiff substrates. Furthermore, FSTF films can be fabricated on flexible substrates (e.g., polyethylene terephthalate (PET)) with similar high colour contrast shown as on the silicon substrates. Wide viewing-angle colour stability was examined in a bending test, and uniform colour was observed without detectable change, showing possibilities of the DLA architecture in accordance with the present embodiments for colour independent flexible vitalization technologies.

[0041] Fabrication of colour-tunable FSTF devices in accordance with the present embodiments that have a multilayer of TiW/Ag/Fe203/IT0 from bottom electrode (BE) to top electrode (TE) structure are presented. A silicon wafer with a ~1 pm thermal oxidized layer and PET were used as the substrates. Layers of 70 nm TiW and 150 nm Ag serving as bottom electrode and the lower functional layer, respectively, were deposited on both rigid and flexible substrates using a magnetron sputter system. Subsequently, Fe ₂ O ₃ with different thicknesses (20 nm, 30 nm, 50 nm, 70 nm and 100 nm) were deposited as the upper functional layer. The transparent top electrode (ITO) was subsequently deposited over the Fe ₂ O ₃ layer. Photo-lithography and lift-off were employed to pattern the FSTF devices. The device size was 50 x 50 pm ² for easy real- time observation. Nanoscale multicolour imaging of the thin films was generated by converting a lithography image on stack into a voltage pattern using a PARK NX 10 atom force microscope (AFM) in a conductive mode. The current and resistance mapping of the patterns were also performed using the CAFM.

[0042] In summary, a paradigm for in- situ generation of active laminar architecture has been established and demonstrated by formation of a floating solid-state thin film and using an electric field. The direct observation by STEM reveals that the unique dynamic configurable features of FSTF architecture, i.e. change of layer order, number and thickness, are driven by the Ag movements under electric fields. Enabled by the floating capability, FSTF exhibits tuneable and high-resolution structural colour in the visible range. Multi-colour prints in a single device are achieved by controlling the operating voltage and stimulation time. Devices, architecture and dynamic color tunability in accordance with the present embodiments has potential applications not only in large panel, zero energy maintenance and high-resolution colour generation technologies, but also in compact photonic and electronic applications, such as displays, wearable devices, and photonic sensors. The DLA tuneable colour technology in accordance with the present embodiments also provides a novel general solid optoelectronic framework for reflective displays, color-tuning technologies, sensors, smart glass, eco-friendly windows, data storage, anti-counterfeiting, colour printing and even arts and decorations. It is noted that the current speed, uniformity and cyclability are mainly limited by the device fabrication process and the interaction of atoms during the altering of structure. Higher speed, cyclability and better uniformity is achievable by refined device fabrication processes and improved structure designs. In addition, the reconfiguration of thin-film architecture as-deposited after fabrication may extend to other fields, relying on static structures of solid-sate devices, including photonic, electronic, magnetic recording, electrochromic, battery, memory and neuromorphic. Further, the concept presented is not exclusive to thin films and controllable structure- altering behaviours in accordance with the present embodiments in other geometries with different applications, such as functional metasurface and tuneable plasmonic structures can apply the same principles as the DLA architecture discussed herein. [0043] While exemplary embodiments have been presented in the foregoing detailed description of the present embodiments, it should be appreciated that a vast number of variations exist. It should further be appreciated that the exemplary embodiments are only examples, and are not intended to limit the scope, applicability, operation, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing exemplary embodiments of the invention, it being understood that various changes may be made in the function and arrangement of steps and method of operation described in the exemplary embodiments without departing from the scope of the invention as set forth in the appended claims.