Study of Low Temperature Deposition of Nanocrystalline Diamond Films on ZnO/LiNbO₃ Layered Structures Suitable for Waveguiding Layer Acoustic Wave Devices

Abstract

In this article, the nanocrystalline diamond (NCD) film low temperature deposition process on ZnO/Si, ZnO/LiNbO3, and ZnO/IDTs/LiNbO3 substrates is investigated aiming at obtaining layered structures suitable for waveguiding layer acoustic wave (WLAW) devices. The NCD synthesis is performed at 250 °C by using a distributed antenna array (DAA) microwave system operating in H2/CH4/CO2 gas mixture at low pressure (<1 mbar). Since the ZnO layer is etched during the NCD growth process, the deposition of a thin AlN layer of few hundred nanometers in thickness on the considered substrates is performed and is shown to be effective as a protective layer. Diamond growth on AlN‐coated ZnO/Si substrates emphasizes the ability of the DAA reactor to synthesize NCD films with properties similar to those obtained on silicon substrates. Besides adherent NCD films up to 300 nm thickness are synthesized on AlN‐coated ZnO/LiNbO3 substrates but stress in the layered structure appears during the plasma process. Finally, the feasibility of a NCD/AlN/ZnO/IDTs/LiNbO3 layered structure, suitable for WLAW devices, is successfully demonstrated, even if the NCD film adherence must be further improved on the inter‐digital transducers (IDTs) finger zone.

Synthesis of High Quality Transparent Nanocrystalline Diamond Films on Glass Substrates Using a Distributed Antenna Array Microwave System

“…This is further evidence for the presence of crystalline diamond within the films. Taking the three diffraction peaks of diamond into account and using equation 2, the grain size was estimated around 12 ± 3 nm, which is characteristic of the nanocrystalline structure and comparable to the grain size obtained on silicon or other substrates such as silicon nitride or piezoelectric materials using a DAA microwave system in the considered experimental conditions [21,30,31,46]. As previously reported, the submicrometric aggregates observed at the film surface are then nano-structure ballas-like particles formed of nanometric diamond grains [30,39,47].…”

Effect of the admixture of N2to low pressure, low temperature H2-CH4-CO2microwave plasmas used for large area deposition of nanocrystalline diamond films

“…Among these new technologies, a distributed antenna array (DAA) microwave system composed of a 4 × 4 source planar matrix was designed in order to achieve NCD films at a substrate temperature as low as 100 • C on fourinch wafers. Its efficiency for NCD growth on conventional (silicon) and unconventional substrates such as silicon nitride, AlN/ZnO/IDTs/LiNbO 3 multilayered structures and titanium implants has been demonstrated [4][5][6]. However, such a low temperature process is associated with a very low growth rate of only a few tens of nanometer per hour (nm h −1 ) at the best [7].…”