Thin films still have their outstanding position in photonics and optoelectronics systems and networks due to the irreplaceable characteristics to be provided by the bulk structures [1–3]. Therefore, the research interests to thin films are continuously increased to achieve better characteristics those would develop the performance of the devices based on thin films [4–6].
As thin films are prepared by several different methods and techniques, many options are available for the designers of thin film devices. However, no single method or technique could produce thin films with the best characteristics. Therefore, continuous evaluation of thin films prepared by any method or technique may provide useful data for designers to choose the optimum for their requirements and applications [1, 3].
More than six decades when first thin film heterojunctions were fabricated. Despite, thin film heterojunctions are the basis of the most effective photonic and optoelectronic devices used in many modern technologies, mainly optical communications and biomedical engineering [7–10]. The combination of thin film physics and engineering has established such basis. However, new aspects of this combination are explored to produce new photonic and optoelectronic devices [11, 12].
Titanium dioxide and nickel oxide are among the most common metal oxide semiconductors due to their excellent characteristics clearly shown in the devices fabricated from them [13]. Research works are motivated to use them because of the excellent energy outline formed due to their energy band gaps (3.20 eV for TiO2 and 3.85 eV for NiO) [14, 15]. The different types of electrical conductivity allowed to fabricate pn heterojunctions of very attractive characteristics. Furthermore, they uniquely show some features making them unbeatable by other metal oxide or compound semiconductors. Photocatalytic activity of titanium dioxide and electrochromic behavior of nickel oxide are examples [14].
Nanotechnology has revolutionized the thin film technology as the designers are making use of nanostructures and their features in addition to those of thin films. So, the ultra-fast response, ultra-high reliability, ultra-high efficiency, ultra-high compactness, high reproducibility and low production cost could be achieved at once [7, 8]. Nevertheless, relatively simple ideas and inexpensive developments – those might not be seen before – still possible to design and produce new photonics and optoelectronics [9].
In this work, the multilayer configuration of TiO2/NiO thin film heterojunction is proposed to enhance the spectral response of photonic devices based on such heterostructure.