Layers of BC x N y were produced in a chemical vapour deposition (CVD) process using trimethylamine borane with He, N 2 , and NH 3 , respectively, as precursor. These layers deposited on Si (100) wafers were characterized chemically by X-ray photoelectron spectroscopy (XPS) and synchrotron radiation-based total reflection X-ray fluorescence analysis combined with near-edge X-ray absorption fine structure spectroscopy (TXRF-NEXAFS). As a result, the composition of the material produced without NH 3 is a B-C bonds containing compound with an atomic relation 1 : 1. Adding NH 3 with a partial pressure of up to about 1.3 Pa the product could be identified as B 2 C 2 N. Increasing the partial pressure of NH 3 to 1.7 and 2.1 Pa the product was enriched in nitrogen yielding a compound characterized as h-BCN. In all cases an impurity of oxygen was observed.