## 1 Introduction  
Among the wide class of binary nitrides, the transition metal nitrides (TMN), such as the AlN, SiN, TiN, VN, CrN, ZrN, NbN, MoN, HfN, TaN and WN ZrN films [1], occupy a key-role for their attractive proprieties which are very useful for the production of different industrial products, such as protective coatings in the aerospace field, biomedical devices in the health sector and cutting tools in machinery [2].  
The state of the art realization of increasingly performing ZrN films shows strengths and weaknesses for each laboratory methodology [3], i.e., some being less performant than others in obtaining defect-free structures, but good stoichiometry ratio N:Zr, one to one, as in the case of synthesis routes by wet [4; 5]. A pulsed laser deposition technique instead produces dense and defect-free coatings but with a scarce N/Zr ratio (0.77). PVD depositions (i.e., reactive sputtering deposition, and dual ion beam sputtering) ensures quality films [6], but with a contamination of oxygen also at a high temperature of the substrate supporting the deposited film. HIPIMS and DCMS have been compared [7] for the case of the binary TiN system and a better performance of HIPIMS respect to DCMS came out. The publications of the last five years about TMNs films presented properties primarily dependent on the deposition method employed, partly by the working parameters [8; 9; 10], PVD or CVD [11; 12; 13] and also with original deposition methods for ZrN.  
The misconception, often reported in the literature with covertly negative sentences, is that quantitative XPS analyses cannot be possible, whereas qualitative and semiquantitative XPS considerations sound more reliable because they are unaffected by data manipulation, which raises some disagreement. Quantitative XPS is in fact a very powerful aspect of data analyses, which needs good knowledge of the spectrometer components and their performances, long experience of data processing and finally good planning of the experimental campaign to produce data storage of high quality. The rather recently acquired BPDMS apparatus gave the authors the confirmation that among the deposition methods employed in the past, the new one can realize oxygen-free stoichiometric ZrN films. For further details about DPMDS it is suggested to refer to the authors' previous works. It was the groundwork for what has now become a comprehensive quantitative procedure study of ZrN films.  
In the present paper, we are going to introduce quantitative chemical results, using XPS, obtained from three groups of ZrN films through accurate experimental and analytical procedures. Following the suggestions of [PERSON] et al. [14], an area correction, after the Shirley background subtraction, has been carried out with three typologies of sensitivity factors: (1) [PERSON] tabulated sensitivity factors (SF), (2) theorical SF tabulated for Al mono source, and finally (3) experimental tabulated SF reported in PHI handbook of VersaProbeII 5000 Spectrometer (omitted results). The use of e-RSF of PHI Handbook were considered the most appropriate values to introduce in the narrow quantitative window of CasaXPS. Ar+ mild sputtering was fruitful in obtaining the chemical composition along the thickness of the samples and it was experimentally verified that it was preferable to the Ar+ 2500 cluster gun. The average stoichiometry of six of the ten specimens under investigation has resulted in the N/Zr being equal to 0.9.