*2.4. ERP Systems and the Technology Acceptance Model*

Organizations are implementing ERP systems to increase productivity as well as turn out to be more responsive. As several studies have revealed, one reason for ERP systems implementation disasters can be recognized as employees' unwillingness to accept and use an implemented ERP system [25,66–69]. Huang and Yasuda [67], in their wide-ranging study of 86 surveyed scientific papers on ERP subjects, indicated that many scientific papers deal with the pre-implementation phase combined with the implementation phase of ERP implementation, but postimplementation studies are seldom. Schlichter and Kraemmergaard [69], in their wide-ranging study of 885 peer-assessed abstracts of journals, also showed a study about the optimization of ERP systems which indicated that post-implementation, usefulness, the accomplishment of competitive benefit through ERP systems, ERP systems employees, and the financial benefits of ERP systems should all be assessed. Several other researchers also indicated the issue of the low utilization of ERP systems, i.e., employees do not take advantage of the implemented ERP system at a higher

stage [21,25,32,66,68,70–72]. Therefore, researchers have focused their research attempts on the acceptance of ERP systems by employees in companies to study circumstances that lead to the use of EPR systems at an advanced level.

Several theoretical models are known for researching the acceptance and use of information systems and information technology (IS/IT) in general. The most often used theoretical theories and models are the "theory of planned behavior" [73], the "theory of reasoned action" [74], the "technology acceptance model (TAM)" [75,76], the "innovation diffusion theory" [77], the "technology–organization–environment model" [78], the "unified theory of acceptance and use of technology" [79,80], etc. (see [27,81]). Among them, the TAM proved to be very promising for researching different viewpoints of ERP systems acceptance and the use by of these systems by users (employees) in companies [22,27,32–35,64,82–84]. The TAM, defined and verified by Davies, is well established and tested in numerous studies (for the latest research, see [27]). Therefore, TAM was used as a research model in several research studies conducted in the past 10 years. Among others, the most important research studies were conducted by Costa et al. [32], Scholtz et al. [71], Calisir et al. [72], Mayeh et al. [83], Shih and Huang [85], Youngberg et al. [86], Erasmus et al. [87], Klaus and Changchit [88], Putri et al. [89], Grandón et al. [90], Koksalmis and Damar [91], etc. These researchers have, in their research studies, experimented with the TAM model by developing TAM model extensions and modifications.

The structure of the TAM is as follows: construct perceived usefulness (PU) and construct perceived ease of use (PEOU) represent the most relevant beliefs for systems and technology (the ERPs) acceptance by users [75]. The construct PU is defined as *'the degree to which a person believes that using a particular system would enhance his or her job performance*' [75], p. 320. In contrast, the construct PEOU refers to *'the degree to which a person believes that using a particular system would be free of an effort'* [75], p. 320. According to TAM, construct PU and construct PEOU have a positive effect on the construct user's attitude (AT) regarding using a system or technology, which further affects the construct user's behavioral intention (BI) to use it. The stronger the intentions to use the system or technology, the higher the level of actual use (U). TAM also includes the expected impact of the construct PEOU on the construct PU [76].

Lately, when researching ERP acceptance, models have been developed that expand the described TAM with various external constructs, especially with constructs considered as antecedents of construct PEOU and construct PU, such as Venkatesh and Davis's TAM 2 [92], the model of the determinants of construct PEOU by Venkatesh [93], and TAM 3 developed by Venkatesh and Bala [94]. The research model, presented in this paper, was extended with the external constructs, that proved important by Sternad et al. [33–35]: organizational process characteristics (OPC), system and technological characteristics (STC) and personal characteristics with the information literacy (PCIL). These are affecting the construct PU and the construct PEOU.

An additional external construct, namely perceived work compatibility (WC), was included in our research model, seen as the employees' perception of fit between the ERP system used and employees' motivation to use it, regardless of the confirmed suitability [82] and refers to the level to which the ERP system enables the employees to perform their working duties using the implemented ERP system. Additionally, the TAM research model in our case was redesigned by replacing the constructs BI and U with extended use (ExU), since our research case focuses on factors affecting the present-day use of ERP systems in the maturity phase. The construct ExU was initially proposed by Hsieh and Wang [95] in their studies. ExU is defined as the usage which exceeds the average, normal use and can guide to a higher quality of the results and benefits [95]. ExU, therefore, refers to the complexity and in-depth use and frequency of using different ERP functionalities [27,30,31,34,35,41,64,77–81,83,92–94,96–98].

The relationships associated with these additional constructs (WC and EXU) are as follows: construct WC influences construct PU [82,96]; that is, with the increased perceived fit of the ERP system to the job needs the perceived usefulness increases, as well. A wellfounded assumption may also be set regarding the direct impact of the construct WC on the construct AT and on the construct ExU. Suppose ERP users perceive that the system increases compatibility with their everyday duties. In that case, they gain an expanded positive posture toward using that system, including its extended use [26,34,35,76]. The research model is further defined in the next section and presented in Figure 3.
