**5.1** Masks preparation and electrodes deposition

Preparation of the masks used for depositing the electrodes in the gas sensor, where these masks are made of steel material in the form of a single clip. The space between every two fingers of the clamp is (400*μm*Þ and the width of the fingers of the clamp is (400*μm*Þ. Each piece includes five fingers its length is (3.3*mm*) and there is an active distance after the preparation of the masks, it is installed on the front part of the floors on which the material films are deposited to deposit the electrodes on top of it by thermal evaporation under vacuum conditions using a purity aluminum wire (99.9%) where the sedimentation takes place under pressure is shown in **Figure 5.**
