A glow plug has a heating element and a ceramic silicon nitride tip which has an outer surface. A low porosity refractory metal oxide coating covers at least a portion of the tip outer surface. A catalyst wire, with a diameter of 0.008 inches, is wrapped about and connected to the coated glow plug tip. The wire is formed of one of the platinum group metals and the wire is free of charge carrying connection to a power source.

Disclosed is a thin film circuit substrate which comprises an electrically insulating substrate, and at least one conductor layer and one protecting layer which are formed on the substrate, the insulating substrate having a surface roughness which is equal to or smaller than 0.1 .mu.Ra when measured as a center line average height. The thin film circuit substrate is suitable for use, for example, in a thermal head.

Disclosed is a thermal printhead made of an insulating substrate, and a heat generating resistor layer formed on the substrate, and wherein the heat generating resistor layer is supplied with electric current. The heat generating resistor layer is made of Cr-Si-SiO alloy, and with the Cr, Si and SiO contents falling within a region defined by points A, B, C and D in a triangular diagram, where the points A, B, C and D are determined as follows:

Disclosed is a thermal head and a method of manufacturing the same, in which a heating portion provided with at least a heating resistor film, a conductor film and a protection film and formed on a substrate having a center-raised stripe and made of an electrically insulating material having anisotropy or selectivity with respect to etching is integrated with a lead wire portion separate from the heating portion and having lead wires formed on an electrically insulating substrate by connecting conductors of the heating portion with respective and corresponding ones of the lead wires of the lead wire portion.

Thin film resistors formed from a metal silicon nitride film are provided in which tungsten, titanium, tantalum, and other group IV A, V A, and VII A metals are included. The silicon to metal ratio varying between about 0.1 and 10.0 and the nitrogen to metal ratio varying between about 0.1 and 10.0 provide sheet resistances which include the useful range of about 100 to over 10,000 ohms per square for films approximately 2,000 angstroms thick. Deposition of these materials by sputtering a metal silicide target in a nitrogen containing atmosphere, such as 20% nitrogen and 80% argon is also provided.