Multicolor Changeable Optical Coating by Adopting Multiple Layers of Ultrathin Phase Change Material Film

The multilayered optical coating whose structure consists of optical cavity and multiple layers of ultrathin phase change material (PCM) film is presented. The color changing is enabled via transition between amorphous and crystalline phases of PCM, which is accompanied by high optical contrast. The phase transition of each PCM layer, separated by ultrathin oxide barrier, can be realized through various crystallization temperatures with respect to the different thickness of ultrathin (<10 nm) PCM film. Accordingly, notable multicolor changing was achieved by thermally or electrically induced selective phase transition of double PCM layers, and its results were compared with transfer-matrix optical modeling. Further evaluation of optical simulations also demonstrated the possibility of increase in expressible colors with increasing number of layers.